diff --git a/backend/migrate_add_session_period_hours.py b/backend/migrate_add_session_period_hours.py
new file mode 100644
index 0000000..5cfb0dc
--- /dev/null
+++ b/backend/migrate_add_session_period_hours.py
@@ -0,0 +1,42 @@
+"""
+Migration: add period_start_hour and period_end_hour to monitoring_sessions.
+
+Run once:
+    python backend/migrate_add_session_period_hours.py
+
+Or inside the container:
+    docker exec terra-view python3 backend/migrate_add_session_period_hours.py
+"""
+
+import sys
+import os
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from backend.database import engine
+from sqlalchemy import text
+
+def run():
+    with engine.connect() as conn:
+        # Check which columns already exist
+        result = conn.execute(text("PRAGMA table_info(monitoring_sessions)"))
+        existing = {row[1] for row in result}
+
+        added = []
+        for col, definition in [
+            ("period_start_hour", "INTEGER"),
+            ("period_end_hour",   "INTEGER"),
+        ]:
+            if col not in existing:
+                conn.execute(text(f"ALTER TABLE monitoring_sessions ADD COLUMN {col} {definition}"))
+                added.append(col)
+            else:
+                print(f"  Column '{col}' already exists — skipping.")
+
+        conn.commit()
+
+        if added:
+            print(f"  Added columns: {', '.join(added)}")
+        print("Migration complete.")
+
+if __name__ == "__main__":
+    run()
diff --git a/backend/models.py b/backend/models.py
index bb0ca10..d6e156d 100644
--- a/backend/models.py
+++ b/backend/models.py
@@ -303,6 +303,12 @@ class MonitoringSession(Base):
     # weekday_day | weekday_night | weekend_day | weekend_night
     period_type = Column(String, nullable=True)
 
+    # Effective monitoring window (hours 0–23).  Night sessions cross midnight
+    # (period_end_hour < period_start_hour).  NULL = no filtering applied.
+    # e.g.  Day: start=7, end=19   Night: start=19, end=7
+    period_start_hour = Column(Integer, nullable=True)
+    period_end_hour   = Column(Integer, nullable=True)
+
     # Snapshot of device configuration at recording time
     session_metadata = Column(Text, nullable=True)  # JSON
 
diff --git a/backend/routers/project_locations.py b/backend/routers/project_locations.py
index 0f10f0e..efa21a8 100644
--- a/backend/routers/project_locations.py
+++ b/backend/routers/project_locations.py
@@ -31,6 +31,7 @@ from backend.models import (
     DataFile,
 )
 from backend.templates_config import templates
+from backend.utils.timezone import local_to_utc
 
 router = APIRouter(prefix="/api/projects/{project_id}", tags=["project-locations"])
 
@@ -824,8 +825,15 @@ async def upload_nrl_data(
             rnh_meta = _parse_rnh(fbytes)
             break
 
-    started_at = _parse_rnh_datetime(rnh_meta.get("start_time_str")) or datetime.utcnow()
-    stopped_at = _parse_rnh_datetime(rnh_meta.get("stop_time_str"))
+    # RNH files store local time (no UTC offset).  Use local values for period
+    # classification / label generation, then convert to UTC for DB storage so
+    # the local_datetime Jinja filter displays the correct time.
+    started_at_local = _parse_rnh_datetime(rnh_meta.get("start_time_str")) or datetime.utcnow()
+    stopped_at_local = _parse_rnh_datetime(rnh_meta.get("stop_time_str"))
+
+    started_at = local_to_utc(started_at_local)
+    stopped_at = local_to_utc(stopped_at_local) if stopped_at_local else None
+
     duration_seconds = None
     if started_at and stopped_at:
         duration_seconds = int((stopped_at - started_at).total_seconds())
@@ -835,8 +843,9 @@ async def upload_nrl_data(
     index_number = rnh_meta.get("index_number", "")
 
     # --- Step 3: Create MonitoringSession ---
-    period_type = _derive_period_type(started_at) if started_at else None
-    session_label = _build_session_label(started_at, location.name, period_type) if started_at else None
+    # Use local times for period/label so classification reflects the clock at the site.
+    period_type = _derive_period_type(started_at_local) if started_at_local else None
+    session_label = _build_session_label(started_at_local, location.name, period_type) if started_at_local else None
 
     session_id = str(uuid.uuid4())
     monitoring_session = MonitoringSession(
diff --git a/backend/routers/projects.py b/backend/routers/projects.py
index 868eb11..e995293 100644
--- a/backend/routers/projects.py
+++ b/backend/routers/projects.py
@@ -1143,7 +1143,7 @@ async def get_project_sessions(
 
     sessions = query.order_by(MonitoringSession.started_at.desc()).all()
 
-    # Enrich with unit and location details
+    # Enrich with unit, location, and effective time window details
     sessions_data = []
     for session in sessions:
         unit = None
@@ -1154,10 +1154,34 @@ async def get_project_sessions(
         if session.location_id:
             location = db.query(MonitoringLocation).filter_by(id=session.location_id).first()
 
+        # Compute "Effective: date time → date time" string when period hours are set
+        effective_range = None
+        if session.period_start_hour is not None and session.period_end_hour is not None and session.started_at:
+            from datetime import date as _date
+            local_start = utc_to_local(session.started_at)
+            start_day = local_start.date()
+            sh = session.period_start_hour
+            eh = session.period_end_hour
+
+            def _fmt_h(h):
+                ampm = "AM" if h < 12 else "PM"
+                h12  = h % 12 or 12
+                return f"{h12}:00 {ampm}"
+
+            start_str = f"{start_day.month}/{start_day.day} {_fmt_h(sh)}"
+            if eh > sh:  # same calendar day
+                end_day = start_day
+            else:        # crosses midnight
+                from datetime import timedelta as _td
+                end_day = start_day + _td(days=1)
+            end_str = f"{end_day.month}/{end_day.day} {_fmt_h(eh)}"
+            effective_range = f"{start_str} → {end_str}"
+
         sessions_data.append({
             "session": session,
             "unit": unit,
             "location": location,
+            "effective_range": effective_range,
         })
 
     return templates.TemplateResponse("partials/projects/session_list.html", {
@@ -1167,6 +1191,125 @@ async def get_project_sessions(
     })
 
 
+@router.get("/{project_id}/sessions-calendar", response_class=HTMLResponse)
+async def get_sessions_calendar(
+    project_id: str,
+    request: Request,
+    db: Session = Depends(get_db),
+    month: Optional[int] = Query(None),
+    year: Optional[int] = Query(None),
+):
+    """
+    Monthly calendar view of monitoring sessions.
+    Color-coded by NRL location.  Returns HTML partial.
+    """
+    from calendar import monthrange
+    from datetime import date as _date, timedelta as _td
+
+    # Default to current month
+    now_local = utc_to_local(datetime.utcnow())
+    if not year:
+        year = now_local.year
+    if not month:
+        month = now_local.month
+
+    # Clamp month to valid range
+    month = max(1, min(12, month))
+
+    # Load all sessions for this project
+    sessions = db.query(MonitoringSession).filter_by(project_id=project_id).all()
+
+    # Build location -> color map (deterministic)
+    PALETTE = [
+        "#f97316", "#3b82f6", "#10b981", "#8b5cf6",
+        "#ec4899", "#14b8a6", "#f59e0b", "#6366f1",
+        "#ef4444", "#84cc16",
+    ]
+    loc_ids = sorted({s.location_id for s in sessions if s.location_id})
+    loc_color = {lid: PALETTE[i % len(PALETTE)] for i, lid in enumerate(loc_ids)}
+
+    # Load location names
+    loc_names = {}
+    for lid in loc_ids:
+        loc = db.query(MonitoringLocation).filter_by(id=lid).first()
+        if loc:
+            loc_names[lid] = loc.name
+
+    # Build day -> list of session dots
+    # day key: date object
+    day_sessions: dict = {}
+    for s in sessions:
+        if not s.started_at:
+            continue
+        local_start = utc_to_local(s.started_at)
+        d = local_start.date()
+        if d.year == year and d.month == month:
+            if d not in day_sessions:
+                day_sessions[d] = []
+            day_sessions[d].append({
+                "session_id": s.id,
+                "label": s.session_label or f"Session {s.id[:8]}",
+                "location_id": s.location_id,
+                "location_name": loc_names.get(s.location_id, "Unknown"),
+                "color": loc_color.get(s.location_id, "#9ca3af"),
+                "status": s.status,
+                "period_type": s.period_type,
+            })
+
+    # Build calendar grid (Mon–Sun weeks)
+    first_day = _date(year, month, 1)
+    last_day = _date(year, month, monthrange(year, month)[1])
+    # Start on Monday before first_day
+    grid_start = first_day - _td(days=first_day.weekday())
+    # End on Sunday after last_day
+    days_after = 6 - last_day.weekday()
+    grid_end = last_day + _td(days=days_after)
+
+    weeks = []
+    cur = grid_start
+    while cur <= grid_end:
+        week = []
+        for _ in range(7):
+            week.append({
+                "date": cur,
+                "in_month": cur.month == month,
+                "is_today": cur == now_local.date(),
+                "sessions": day_sessions.get(cur, []),
+            })
+            cur += _td(days=1)
+        weeks.append(week)
+
+    # Prev/next month navigation
+    prev_month = month - 1 if month > 1 else 12
+    prev_year  = year if month > 1 else year - 1
+    next_month = month + 1 if month < 12 else 1
+    next_year  = year if month < 12 else year + 1
+
+    import calendar as _cal
+    month_name = _cal.month_name[month]
+
+    # Legend: only locations that have sessions this month
+    used_lids = {s["location_id"] for day in day_sessions.values() for s in day}
+    legend = [
+        {"location_id": lid, "name": loc_names.get(lid, lid[:8]), "color": loc_color[lid]}
+        for lid in loc_ids if lid in used_lids
+    ]
+
+    return templates.TemplateResponse("partials/projects/sessions_calendar.html", {
+        "request": request,
+        "project_id": project_id,
+        "weeks": weeks,
+        "month": month,
+        "year": year,
+        "month_name": month_name,
+        "prev_month": prev_month,
+        "prev_year": prev_year,
+        "next_month": next_month,
+        "next_year": next_year,
+        "legend": legend,
+    })
+
+
 @router.get("/{project_id}/ftp-browser", response_class=HTMLResponse)
 async def get_ftp_browser(
     project_id: str,
@@ -1903,8 +2046,98 @@ async def patch_session(
             raise HTTPException(status_code=400, detail=f"Invalid period_type. Must be one of: {', '.join(sorted(VALID_PERIOD_TYPES))}")
         session.period_type = pt or None
 
+    # Configurable period window (0–23 integers; null = no filter)
+    for field in ("period_start_hour", "period_end_hour"):
+        if field in data:
+            val = data[field]
+            if val is None or val == "":
+                setattr(session, field, None)
+            else:
+                try:
+                    h = int(val)
+                    if not (0 <= h <= 23):
+                        raise ValueError
+                    setattr(session, field, h)
+                except (ValueError, TypeError):
+                    raise HTTPException(status_code=400, detail=f"{field} must be an integer 0–23 or null")
+
     db.commit()
-    return JSONResponse({"status": "success", "session_label": session.session_label, "period_type": session.period_type})
+    return JSONResponse({
+        "status": "success",
+        "session_label": session.session_label,
+        "period_type": session.period_type,
+        "period_start_hour": session.period_start_hour,
+        "period_end_hour": session.period_end_hour,
+    })
+
+
+@router.get("/{project_id}/sessions/{session_id}/detail", response_class=HTMLResponse)
+async def view_session_detail(
+    request: Request,
+    project_id: str,
+    session_id: str,
+    db: Session = Depends(get_db),
+):
+    """
+    Session detail page: shows files, editable session info, data preview, and report actions.
+    """
+    from backend.models import DataFile
+    from pathlib import Path
+
+    project = db.query(Project).filter_by(id=project_id).first()
+    if not project:
+        raise HTTPException(status_code=404, detail="Project not found")
+    _require_sound_project(project)
+
+    session = db.query(MonitoringSession).filter_by(id=session_id, project_id=project_id).first()
+    if not session:
+        raise HTTPException(status_code=404, detail="Session not found")
+
+    location = db.query(MonitoringLocation).filter_by(id=session.location_id).first() if session.location_id else None
+    unit = db.query(RosterUnit).filter_by(id=session.unit_id).first() if session.unit_id else None
+
+    # Load all data files for this session
+    files = db.query(DataFile).filter_by(session_id=session_id).order_by(DataFile.created_at).all()
+
+    # Compute effective time range string for display
+    effective_range = None
+    if session.period_start_hour is not None and session.period_end_hour is not None and session.started_at:
+        local_start = utc_to_local(session.started_at)
+        start_day = local_start.date()
+        sh = session.period_start_hour
+        eh = session.period_end_hour
+        def _fmt_h(h):
+            ampm = "AM" if h < 12 else "PM"
+            h12 = h % 12 or 12
+            return f"{h12}:00 {ampm}"
+        start_str = f"{start_day.month}/{start_day.day} {_fmt_h(sh)}"
+        if eh > sh:
+            end_day = start_day
+        else:
+            from datetime import timedelta as _td
+            end_day = start_day + _td(days=1)
+        end_str = f"{end_day.month}/{end_day.day} {_fmt_h(eh)}"
+        effective_range = f"{start_str} → {end_str}"
+
+    # Parse session_metadata if present
+    session_meta = {}
+    if session.session_metadata:
+        try:
+            session_meta = json.loads(session.session_metadata)
+        except Exception:
+            pass
+
+    return templates.TemplateResponse("session_detail.html", {
+        "request": request,
+        "project": project,
+        "project_id": project_id,
+        "session": session,
+        "location": location,
+        "unit": unit,
+        "files": files,
+        "effective_range": effective_range,
+        "session_meta": session_meta,
+    })
 
 
 @router.get("/{project_id}/files/{file_id}/view-rnd", response_class=HTMLResponse)
@@ -1971,6 +2204,8 @@ async def view_rnd_file(
         "metadata": metadata,
         "filename": file_path.name,
         "is_leq": _is_leq_file(str(file_record.file_path), _peek_rnd_headers(file_path)),
+        "period_start_hour": session.period_start_hour,
+        "period_end_hour": session.period_end_hour,
     })
 
 
@@ -2080,6 +2315,8 @@ async def get_rnd_data(
             "summary": summary,
             "headers": summary["headers"],
             "data": rows,
+            "period_start_hour": session.period_start_hour,
+            "period_end_hour": session.period_end_hour,
         }
 
     except Exception as e:
@@ -3511,6 +3748,8 @@ def _build_location_data_from_sessions(project_id: str, db, selected_session_ids
             "loc_name": loc_name,
             "session_label": session.session_label or "",
             "period_type": session.period_type or "",
+            "period_start_hour": session.period_start_hour,
+            "period_end_hour": session.period_end_hour,
             "started_at": session.started_at,
             "rows": [],
         }
@@ -3552,25 +3791,36 @@ def _build_location_data_from_sessions(project_id: str, db, selected_session_ids
                     pass
             parsed.append((dt, row))
 
-        # Determine which rows to keep based on period_type
-        is_day_session = period_type in ('weekday_day', 'weekend_day')
+        # Determine effective hour window.
+        # Prefer per-session period_start/end_hour; fall back to hardcoded defaults.
+        sh = entry.get("period_start_hour")  # e.g. 7 for Day, 19 for Night
+        eh = entry.get("period_end_hour")    # e.g. 19 for Day,  7 for Night
+        if sh is None or eh is None:
+            # Legacy defaults based on period_type
+            is_day_session = period_type in ('weekday_day', 'weekend_day')
+            sh = 7 if is_day_session else 19
+            eh = 19 if is_day_session else 7
+        else:
+            is_day_session = eh > sh  # crosses midnight when end < start
+
         target_date = None
         if is_day_session:
-            # Day: 07:00–18:59 only, restricted to the LAST calendar date that has daytime rows
+            # Day-style: start_h <= hour < end_h, restricted to the LAST calendar date
+            in_window = lambda h: sh <= h < eh
             daytime_dates = sorted({
-                dt.date() for dt, row in parsed
-                if dt and 7 <= dt.hour < 19
+                dt.date() for dt, row in parsed if dt and in_window(dt.hour)
             })
             target_date = daytime_dates[-1] if daytime_dates else None
             filtered = [
                 (dt, row) for dt, row in parsed
-                if dt and dt.date() == target_date and 7 <= dt.hour < 19
+                if dt and dt.date() == target_date and in_window(dt.hour)
             ]
         else:
-            # Night: 19:00–06:59, spanning both calendar days — no date restriction
+            # Night-style: hour >= start_h OR hour < end_h (crosses midnight)
+            in_window = lambda h: h >= sh or h < eh
             filtered = [
                 (dt, row) for dt, row in parsed
-                if dt and (dt.hour >= 19 or dt.hour < 7)
+                if dt and in_window(dt.hour)
             ]
 
         # Fall back to all rows if filtering removed everything
diff --git a/backend/templates_config.py b/backend/templates_config.py
index d1c7360..96a871f 100644
--- a/backend/templates_config.py
+++ b/backend/templates_config.py
@@ -73,10 +73,16 @@ def jinja_log_tail_display(s):
         return str(s)
 
 
+def jinja_local_datetime_input(dt):
+    """Jinja filter: format UTC datetime as local YYYY-MM-DDTHH:MM for <input type='datetime-local'>."""
+    return format_local_datetime(dt, "%Y-%m-%dT%H:%M")
+
+
 # Register Jinja filters and globals
 templates.env.filters["local_datetime"] = jinja_local_datetime
 templates.env.filters["local_time"] = jinja_local_time
 templates.env.filters["local_date"] = jinja_local_date
+templates.env.filters["local_datetime_input"] = jinja_local_datetime_input
 templates.env.filters["fromjson"] = jinja_fromjson
 templates.env.globals["timezone_abbr"] = jinja_timezone_abbr
 templates.env.globals["get_user_timezone"] = get_user_timezone
diff --git a/templates/partials/projects/session_list.html b/templates/partials/projects/session_list.html
index 6b8b617..2886855 100644
--- a/templates/partials/projects/session_list.html
+++ b/templates/partials/projects/session_list.html
@@ -5,6 +5,7 @@
         {% set s = item.session %}
         {% set loc = item.location %}
         {% set unit = item.unit %}
+        {% set effective_range = item.effective_range %}
 
         {# Period display maps #}
         {% set period_labels = {
@@ -49,25 +50,74 @@
                             <span class="px-2 py-0.5 text-xs font-medium bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-400 rounded-full">Failed</span>
                         {% endif %}
 
-                        <!-- Period type badge (click to change) -->
+                        <!-- Period type badge (click to open hour editor) -->
                         <div class="relative" id="period-wrap-{{ s.id }}">
-                            <button onclick="togglePeriodMenu('{{ s.id }}')"
+                            <button onclick="openPeriodEditor('{{ s.id }}')"
                                     id="period-badge-{{ s.id }}"
                                     class="px-2 py-0.5 text-xs font-medium rounded-full flex items-center gap-1 transition-colors {{ period_colors.get(s.period_type, 'bg-gray-100 text-gray-500 dark:bg-gray-700 dark:text-gray-400') }}"
-                                    title="Click to change period type">
+                                    title="Click to edit period type and hours">
                                 <span id="period-label-{{ s.id }}">{{ period_labels.get(s.period_type, 'Set period') }}</span>
                                 <svg class="w-3 h-3 opacity-60 shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                                     <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7"></path>
                                 </svg>
                             </button>
-                            <div id="period-menu-{{ s.id }}"
-                                 class="hidden absolute left-0 top-full mt-1 z-20 bg-white dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg shadow-lg min-w-[160px] py-1">
-                                {% for pt, pt_label in [('weekday_day','Weekday Day'),('weekday_night','Weekday Night'),('weekend_day','Weekend Day'),('weekend_night','Weekend Night')] %}
-                                <button onclick="setPeriodType('{{ s.id }}', '{{ pt }}')"
-                                        class="w-full text-left px-3 py-1.5 text-xs hover:bg-gray-100 dark:hover:bg-slate-600 text-gray-700 dark:text-gray-300 {% if s.period_type == pt %}font-bold{% endif %}">
-                                    {{ pt_label }}
-                                </button>
-                                {% endfor %}
+
+                            <!-- Period editor panel -->
+                            <div id="period-editor-{{ s.id }}"
+                                 class="hidden absolute left-0 top-full mt-1 z-20 bg-white dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg shadow-lg w-64 p-3 space-y-3">
+
+                                <!-- Period type selector -->
+                                <div>
+                                    <label class="block text-xs font-medium text-gray-600 dark:text-gray-400 mb-1">Period Type</label>
+                                    <div class="grid grid-cols-2 gap-1">
+                                        {% for pt, pt_label in [('weekday_day','WD Day'),('weekday_night','WD Night'),('weekend_day','WE Day'),('weekend_night','WE Night')] %}
+                                        <button onclick="selectPeriodType('{{ s.id }}', '{{ pt }}')"
+                                                id="pt-btn-{{ s.id }}-{{ pt }}"
+                                                class="period-type-btn text-xs py-1 px-2 rounded border transition-colors
+                                                       {% if s.period_type == pt %}border-seismo-orange bg-orange-50 text-seismo-orange dark:bg-orange-900/20{% else %}border-gray-200 dark:border-gray-600 text-gray-600 dark:text-gray-400 hover:border-gray-400{% endif %}">
+                                            {{ pt_label }}
+                                        </button>
+                                        {% endfor %}
+                                    </div>
+                                </div>
+
+                                <!-- Hour inputs -->
+                                <div class="grid grid-cols-2 gap-2">
+                                    <div>
+                                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">Start Hour (0–23)</label>
+                                        <input type="number" min="0" max="23"
+                                               id="period-start-hr-{{ s.id }}"
+                                               value="{{ s.period_start_hour if s.period_start_hour is not none else '' }}"
+                                               placeholder="e.g. 19"
+                                               class="w-full text-xs bg-gray-50 dark:bg-slate-600 border border-gray-200 dark:border-gray-500 rounded px-2 py-1 text-gray-800 dark:text-gray-200 focus:outline-none focus:border-seismo-orange">
+                                    </div>
+                                    <div>
+                                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">End Hour (0–23)</label>
+                                        <input type="number" min="0" max="23"
+                                               id="period-end-hr-{{ s.id }}"
+                                               value="{{ s.period_end_hour if s.period_end_hour is not none else '' }}"
+                                               placeholder="e.g. 7"
+                                               class="w-full text-xs bg-gray-50 dark:bg-slate-600 border border-gray-200 dark:border-gray-500 rounded px-2 py-1 text-gray-800 dark:text-gray-200 focus:outline-none focus:border-seismo-orange">
+                                    </div>
+                                </div>
+                                <p class="text-xs text-gray-400 dark:text-gray-500">Day: 7→19 · Night: 19→7 · Customize as needed</p>
+
+                                <!-- Actions -->
+                                <div class="flex gap-2 pt-1">
+                                    <button onclick="savePeriodEditor('{{ s.id }}')"
+                                            class="flex-1 text-xs py-1 bg-seismo-orange text-white rounded hover:bg-orange-600 transition-colors">
+                                        Save
+                                    </button>
+                                    <button onclick="closePeriodEditor('{{ s.id }}')"
+                                            class="text-xs py-1 px-2 border border-gray-200 dark:border-gray-600 rounded text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-slate-600 transition-colors">
+                                        Cancel
+                                    </button>
+                                    <button onclick="clearPeriodEditor('{{ s.id }}')"
+                                            class="text-xs py-1 px-2 border border-gray-200 dark:border-gray-600 rounded text-gray-500 dark:text-gray-500 hover:bg-gray-100 dark:hover:bg-slate-600 transition-colors"
+                                            title="Clear period type and hours">
+                                        Clear
+                                    </button>
+                                </div>
                             </div>
                         </div>
                     </div>
@@ -131,8 +181,17 @@
                         {% endif %}
                     </div>
 
-                    {% if s.notes %}
-                    <p class="text-xs text-gray-400 dark:text-gray-500 mt-2 italic">{{ s.notes }}</p>
+                    <!-- Effective window (when period hours are set) -->
+                    {% if effective_range %}
+                    <div class="flex items-center gap-1 mt-1.5 text-xs text-indigo-600 dark:text-indigo-400">
+                        <svg class="w-3.5 h-3.5 shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 8v4l3 3m6-3a9 9 0 11-18 0 9 9 0 0118 0z"></path>
+                        </svg>
+                        <span id="effective-range-{{ s.id }}">Effective: {{ effective_range }}</span>
+                    </div>
+                    {% else %}
+                    <div class="hidden text-xs text-indigo-600 dark:text-indigo-400 mt-1.5"
+                         id="effective-range-{{ s.id }}"></div>
                     {% endif %}
                 </div>
 
@@ -163,6 +222,8 @@
 {% endif %}
 
 <script>
+const PROJECT_ID = '{{ project_id }}';
+
 const PERIOD_COLORS = {
     weekday_day:   'bg-blue-100 text-blue-800 dark:bg-blue-900/30 dark:text-blue-300',
     weekday_night: 'bg-indigo-100 text-indigo-800 dark:bg-indigo-900/30 dark:text-indigo-300',
@@ -175,46 +236,145 @@ const PERIOD_LABELS = {
     weekend_day:   'Weekend Day',
     weekend_night: 'Weekend Night',
 };
+// Default hours for each period type
+const PERIOD_DEFAULT_HOURS = {
+    weekday_day:   {start: 7,  end: 19},
+    weekday_night: {start: 19, end: 7},
+    weekend_day:   {start: 7,  end: 19},
+    weekend_night: {start: 19, end: 7},
+};
 const FALLBACK_COLORS = ['bg-gray-100','text-gray-500','dark:bg-gray-700','dark:text-gray-400'];
 const ALL_BADGE_COLORS = [...new Set([
     ...FALLBACK_COLORS,
     ...Object.values(PERIOD_COLORS).flatMap(s => s.split(' '))
 ])];
 
-function togglePeriodMenu(sessionId) {
-    const menu = document.getElementById('period-menu-' + sessionId);
-    document.querySelectorAll('[id^="period-menu-"]').forEach(m => {
-        if (m.id !== 'period-menu-' + sessionId) m.classList.add('hidden');
+// Track which period type is selected in the editor before saving
+const _editorState = {};
+
+// ---- Period editor ----
+
+function openPeriodEditor(sessionId) {
+    // Close all other editors first
+    document.querySelectorAll('[id^="period-editor-"]').forEach(el => {
+        if (el.id !== 'period-editor-' + sessionId) el.classList.add('hidden');
     });
-    menu.classList.toggle('hidden');
+    document.getElementById('period-editor-' + sessionId).classList.toggle('hidden');
 }
 
+function closePeriodEditor(sessionId) {
+    document.getElementById('period-editor-' + sessionId).classList.add('hidden');
+    delete _editorState[sessionId];
+}
+
+function selectPeriodType(sessionId, pt) {
+    _editorState[sessionId] = pt;
+    // Highlight selected button
+    document.querySelectorAll(`[id^="pt-btn-${sessionId}-"]`).forEach(btn => {
+        const isSelected = btn.id === `pt-btn-${sessionId}-${pt}`;
+        btn.classList.toggle('border-seismo-orange', isSelected);
+        btn.classList.toggle('bg-orange-50', isSelected);
+        btn.classList.toggle('text-seismo-orange', isSelected);
+        btn.classList.toggle('dark:bg-orange-900/20', isSelected);
+        btn.classList.toggle('border-gray-200', !isSelected);
+        btn.classList.toggle('dark:border-gray-600', !isSelected);
+        btn.classList.toggle('text-gray-600', !isSelected);
+        btn.classList.toggle('dark:text-gray-400', !isSelected);
+    });
+    // Fill default hours
+    const defaults = PERIOD_DEFAULT_HOURS[pt];
+    if (defaults) {
+        const sh = document.getElementById('period-start-hr-' + sessionId);
+        const eh = document.getElementById('period-end-hr-' + sessionId);
+        if (sh && !sh.value) sh.value = defaults.start;
+        if (eh && !eh.value) eh.value = defaults.end;
+    }
+}
+
+async function savePeriodEditor(sessionId) {
+    const pt = _editorState[sessionId] || document.getElementById('period-badge-' + sessionId)
+                                           ?.dataset?.currentPeriod || null;
+    const shInput = document.getElementById('period-start-hr-' + sessionId);
+    const ehInput = document.getElementById('period-end-hr-' + sessionId);
+
+    const payload = {};
+    if (pt !== undefined) payload.period_type = pt || null;
+    payload.period_start_hour = shInput?.value !== '' ? parseInt(shInput.value, 10) : null;
+    payload.period_end_hour   = ehInput?.value !== '' ? parseInt(ehInput.value, 10) : null;
+
+    try {
+        const resp = await fetch(`/api/projects/${PROJECT_ID}/sessions/${sessionId}`, {
+            method: 'PATCH',
+            headers: {'Content-Type': 'application/json'},
+            body: JSON.stringify(payload),
+        });
+        if (!resp.ok) throw new Error(await resp.text());
+        const result = await resp.json();
+
+        // Update badge
+        const badge = document.getElementById('period-badge-' + sessionId);
+        const label = document.getElementById('period-label-' + sessionId);
+        const newPt = result.period_type;
+        ALL_BADGE_COLORS.forEach(c => badge.classList.remove(c));
+        if (newPt && PERIOD_COLORS[newPt]) {
+            badge.classList.add(...PERIOD_COLORS[newPt].split(' ').filter(Boolean));
+            if (label) label.textContent = PERIOD_LABELS[newPt];
+        } else {
+            badge.classList.add(...FALLBACK_COLORS);
+            if (label) label.textContent = 'Set period';
+        }
+
+        // Update effective range display
+        _updateEffectiveRange(sessionId, result.period_start_hour, result.period_end_hour);
+
+        closePeriodEditor(sessionId);
+    } catch (err) {
+        alert('Failed to save period: ' + err.message);
+    }
+}
+
+async function clearPeriodEditor(sessionId) {
+    const shInput = document.getElementById('period-start-hr-' + sessionId);
+    const ehInput = document.getElementById('period-end-hr-' + sessionId);
+    if (shInput) shInput.value = '';
+    if (ehInput) ehInput.value = '';
+    _editorState[sessionId] = null;
+
+    // Reset period type button highlights
+    document.querySelectorAll(`[id^="pt-btn-${sessionId}-"]`).forEach(btn => {
+        btn.classList.remove('border-seismo-orange','bg-orange-50','text-seismo-orange','dark:bg-orange-900/20');
+        btn.classList.add('border-gray-200','dark:border-gray-600','text-gray-600','dark:text-gray-400');
+    });
+}
+
+// ---- Effective range helper ----
+
+function _updateEffectiveRange(sessionId, startHour, endHour) {
+    const el = document.getElementById('effective-range-' + sessionId);
+    if (!el) return;
+    if (startHour == null || endHour == null) {
+        el.textContent = '';
+        el.classList.add('hidden');
+        return;
+    }
+    function _fmt(h) {
+        const ampm = h < 12 ? 'AM' : 'PM';
+        const h12 = h % 12 || 12;
+        return `${h12}:00 ${ampm}`;
+    }
+    // We don't have the session start date in JS so just show the hours pattern
+    el.textContent = `Effective window: ${_fmt(startHour)} → ${_fmt(endHour)}`;
+    el.classList.remove('hidden');
+}
+
+// ---- Close editors on outside click ----
 document.addEventListener('click', function(e) {
     if (!e.target.closest('[id^="period-wrap-"]')) {
-        document.querySelectorAll('[id^="period-menu-"]').forEach(m => m.classList.add('hidden'));
+        document.querySelectorAll('[id^="period-editor-"]').forEach(m => m.classList.add('hidden'));
     }
 });
 
-async function setPeriodType(sessionId, periodType) {
-    document.getElementById('period-menu-' + sessionId).classList.add('hidden');
-    const badge = document.getElementById('period-badge-' + sessionId);
-    badge.disabled = true;
-    try {
-        const resp = await fetch(`/api/projects/{{ project_id }}/sessions/${sessionId}`, {
-            method: 'PATCH',
-            headers: {'Content-Type': 'application/json'},
-            body: JSON.stringify({period_type: periodType}),
-        });
-        if (!resp.ok) throw new Error(await resp.text());
-        ALL_BADGE_COLORS.forEach(c => badge.classList.remove(c));
-        badge.classList.add(...(PERIOD_COLORS[periodType] || FALLBACK_COLORS.join(' ')).split(' ').filter(Boolean));
-        document.getElementById('period-label-' + sessionId).textContent = PERIOD_LABELS[periodType] || periodType;
-    } catch(err) {
-        alert('Failed to update period type: ' + err.message);
-    } finally {
-        badge.disabled = false;
-    }
-}
+// ---- Label editing ----
 
 function startEditLabel(sessionId) {
     document.getElementById('label-display-' + sessionId).classList.add('hidden');
@@ -234,7 +394,7 @@ async function saveLabel(sessionId) {
     const input   = document.getElementById('label-input-' + sessionId);
     const newLabel = input.value.trim();
     try {
-        const resp = await fetch(`/api/projects/{{ project_id }}/sessions/${sessionId}`, {
+        const resp = await fetch(`/api/projects/${PROJECT_ID}/sessions/${sessionId}`, {
             method: 'PATCH',
             headers: {'Content-Type': 'application/json'},
             body: JSON.stringify({session_label: newLabel}),
@@ -249,8 +409,10 @@ async function saveLabel(sessionId) {
     }
 }
 
+// ---- Session details ----
+
 function viewSession(sessionId) {
-    alert('Session details coming soon: ' + sessionId);
+    window.location.href = `/api/projects/${PROJECT_ID}/sessions/${sessionId}/detail`;
 }
 
 function stopRecording(sessionId) {
diff --git a/templates/partials/projects/sessions_calendar.html b/templates/partials/projects/sessions_calendar.html
new file mode 100644
index 0000000..feda7d4
--- /dev/null
+++ b/templates/partials/projects/sessions_calendar.html
@@ -0,0 +1,91 @@
+<!-- Monthly Sessions Calendar -->
+<div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 overflow-hidden">
+
+    <!-- Calendar header: month navigation -->
+    <div class="px-5 py-3 border-b border-gray-200 dark:border-gray-700 flex items-center justify-between">
+        <button hx-get="/api/projects/{{ project_id }}/sessions-calendar?month={{ prev_month }}&year={{ prev_year }}"
+                hx-target="#sessions-calendar"
+                hx-swap="innerHTML"
+                class="p-1.5 rounded-lg hover:bg-gray-100 dark:hover:bg-slate-700 transition-colors text-gray-500 dark:text-gray-400"
+                title="Previous month">
+            <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 19l-7-7 7-7"></path>
+            </svg>
+        </button>
+
+        <h3 class="text-sm font-semibold text-gray-800 dark:text-gray-200">{{ month_name }} {{ year }}</h3>
+
+        <button hx-get="/api/projects/{{ project_id }}/sessions-calendar?month={{ next_month }}&year={{ next_year }}"
+                hx-target="#sessions-calendar"
+                hx-swap="innerHTML"
+                class="p-1.5 rounded-lg hover:bg-gray-100 dark:hover:bg-slate-700 transition-colors text-gray-500 dark:text-gray-400"
+                title="Next month">
+            <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"></path>
+            </svg>
+        </button>
+    </div>
+
+    <!-- Legend -->
+    {% if legend %}
+    <div class="px-5 py-2 border-b border-gray-100 dark:border-gray-700 flex flex-wrap gap-3">
+        {% for loc in legend %}
+        <div class="flex items-center gap-1.5 text-xs text-gray-600 dark:text-gray-400">
+            <span class="w-2.5 h-2.5 rounded-full shrink-0" style="background-color: {{ loc.color }}"></span>
+            <span>{{ loc.name }}</span>
+        </div>
+        {% endfor %}
+    </div>
+    {% endif %}
+
+    <!-- Day-of-week headers -->
+    <div class="grid grid-cols-7 border-b border-gray-100 dark:border-gray-700">
+        {% for day_name in ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'] %}
+        <div class="py-2 text-center text-xs font-medium text-gray-400 dark:text-gray-500 uppercase tracking-wide
+                    {% if loop.index >= 6 %}text-amber-500 dark:text-amber-400{% endif %}">
+            {{ day_name }}
+        </div>
+        {% endfor %}
+    </div>
+
+    <!-- Calendar grid -->
+    {% for week in weeks %}
+    <div class="grid grid-cols-7 {% if not loop.last %}border-b border-gray-100 dark:border-gray-700{% endif %}">
+        {% for day in week %}
+        <div class="min-h-[72px] p-1.5 {% if not loop.last %}border-r border-gray-100 dark:border-gray-700{% endif %}
+                    {% if not day.in_month %}bg-gray-50 dark:bg-slate-800/50{% else %}bg-white dark:bg-slate-800{% endif %}
+                    {% if day.is_today %}ring-1 ring-inset ring-seismo-orange{% endif %}">
+
+            <!-- Date number -->
+            <div class="text-right mb-1">
+                <span class="text-xs {% if day.is_today %}font-bold text-seismo-orange{% elif day.in_month %}text-gray-700 dark:text-gray-300{% else %}text-gray-300 dark:text-gray-600{% endif %}">
+                    {{ day.date.day }}
+                </span>
+            </div>
+
+            <!-- Session dots/chips -->
+            {% if day.sessions %}
+            <div class="space-y-0.5">
+                {% for s in day.sessions[:4] %}
+                <a href="/api/projects/{{ project_id }}/sessions/{{ s.session_id }}/detail"
+                   class="flex items-center gap-1 px-1 py-0.5 rounded text-xs truncate hover:opacity-80 transition-opacity"
+                   style="background-color: {{ s.color }}22; border-left: 2px solid {{ s.color }};"
+                   title="{{ s.label }}">
+                    <span class="truncate text-gray-700 dark:text-gray-300" style="color: {{ s.color }}; font-size: 0.65rem; line-height: 1.2;">
+                        {{ s.location_name }}
+                        {% if s.period_type %}
+                        <span class="opacity-60">{{ '☀' if 'day' in s.period_type else '☾' }}</span>
+                        {% endif %}
+                    </span>
+                </a>
+                {% endfor %}
+                {% if day.sessions|length > 4 %}
+                <div class="text-center text-xs text-gray-400 dark:text-gray-500">+{{ day.sessions|length - 4 }} more</div>
+                {% endif %}
+            </div>
+            {% endif %}
+        </div>
+        {% endfor %}
+    </div>
+    {% endfor %}
+</div>
diff --git a/templates/projects/detail.html b/templates/projects/detail.html
index d559017..26f2200 100644
--- a/templates/projects/detail.html
+++ b/templates/projects/detail.html
@@ -208,6 +208,19 @@
                 <div class="text-center py-8 text-gray-500">Loading sessions...</div>
             </div>
         </div>
+
+        <!-- Monthly Calendar -->
+        <div class="mt-6 bg-white dark:bg-slate-800 rounded-xl shadow-lg p-6">
+            <div class="flex items-center justify-between mb-4">
+                <h3 class="text-lg font-semibold text-gray-900 dark:text-white">Calendar View</h3>
+            </div>
+            <div id="sessions-calendar"
+                 hx-get="/api/projects/{{ project_id }}/sessions-calendar"
+                 hx-trigger="load"
+                 hx-swap="innerHTML">
+                <div class="text-center py-6 text-gray-400 text-sm">Loading calendar…</div>
+            </div>
+        </div>
     </div>
 
     <!-- Data Files Tab -->
diff --git a/templates/rnd_viewer.html b/templates/rnd_viewer.html
index 95ca840..507c3f8 100644
--- a/templates/rnd_viewer.html
+++ b/templates/rnd_viewer.html
@@ -181,6 +181,27 @@ let chartInstance = null;
 let allData = [];
 let allHeaders = [];
 
+// Session period window (null = no filtering)
+const SESSION_PERIOD_START_HOUR = {{ period_start_hour if period_start_hour is not none else 'null' }};
+const SESSION_PERIOD_END_HOUR   = {{ period_end_hour if period_end_hour is not none else 'null' }};
+
+/**
+ * Returns true if the given hour integer is within the session's period window.
+ * Always returns true when no period window is configured.
+ */
+function _isInPeriodWindow(hour) {
+    if (SESSION_PERIOD_START_HOUR === null || SESSION_PERIOD_END_HOUR === null) return true;
+    const sh = SESSION_PERIOD_START_HOUR;
+    const eh = SESSION_PERIOD_END_HOUR;
+    if (eh > sh) {
+        // Same-day window, e.g. 7–19
+        return hour >= sh && hour < eh;
+    } else {
+        // Crosses midnight, e.g. 19–7
+        return hour >= sh || hour < eh;
+    }
+}
+
 // Load data on page load
 document.addEventListener('DOMContentLoaded', function() {
     loadRndData();
@@ -387,19 +408,21 @@ function renderChart(data, fileType) {
     });
 }
 
-function renderTable(headers, data) {
-    const headerRow = document.getElementById('table-header');
-    const tbody = document.getElementById('table-body');
+function _rowHour(row) {
+    // Parse hour from "Start Time" field (format: "YYYY/MM/DD HH:MM:SS")
+    const t = row['Start Time'];
+    if (!t) return null;
+    const parts = t.split(' ');
+    if (parts.length < 2) return null;
+    return parseInt(parts[1].split(':')[0], 10);
+}
 
-    // Render headers
-    headerRow.innerHTML = '<tr>' + headers.map(h =>
-        `<th class="px-4 py-3 text-left font-medium">${escapeHtml(h)}</th>`
-    ).join('') + '</tr>';
-
-    // Render rows (limit to first 500 for performance)
-    const displayData = data.slice(0, 500);
-    tbody.innerHTML = displayData.map(row =>
-        '<tr class="hover:bg-gray-50 dark:hover:bg-gray-800/50">' +
+function _buildRow(headers, row) {
+    const hour = _rowHour(row);
+    const inWindow = hour === null || _isInPeriodWindow(hour);
+    const dimClass = inWindow ? '' : 'opacity-40';
+    const titleAttr = (!inWindow) ? ' title="Outside period window"' : '';
+    return `<tr class="hover:bg-gray-50 dark:hover:bg-gray-800/50 ${dimClass}"${titleAttr}>` +
         headers.map(h => {
             const val = row[h];
             let displayVal = val;
@@ -410,12 +433,34 @@ function renderTable(headers, data) {
             }
             return `<td class="px-4 py-2 text-gray-700 dark:text-gray-300">${escapeHtml(String(displayVal))}</td>`;
         }).join('') +
-        '</tr>'
-    ).join('');
+        '</tr>';
+}
+
+function renderTable(headers, data) {
+    const headerRow = document.getElementById('table-header');
+    const tbody = document.getElementById('table-body');
+
+    // Render headers — add period window indicator if configured
+    let periodNote = '';
+    if (SESSION_PERIOD_START_HOUR !== null && SESSION_PERIOD_END_HOUR !== null) {
+        function _fmtH(h) { const ampm = h < 12 ? 'AM' : 'PM'; return `${h%12||12}:00 ${ampm}`; }
+        periodNote = ` <span class="ml-2 text-indigo-500 dark:text-indigo-400 font-normal normal-case text-xs" title="Dimmed rows are outside this window">Period: ${_fmtH(SESSION_PERIOD_START_HOUR)} → ${_fmtH(SESSION_PERIOD_END_HOUR)}</span>`;
+    }
+    headerRow.innerHTML = '<tr>' + headers.map((h, i) =>
+        `<th class="px-4 py-3 text-left font-medium">${escapeHtml(h)}${i === 0 ? periodNote : ''}</th>`
+    ).join('') + '</tr>';
+
+    // Render rows (limit to first 500 for performance)
+    const displayData = data.slice(0, 500);
+    tbody.innerHTML = displayData.map(row => _buildRow(headers, row)).join('');
 
     // Update row count
+    const inWindowCount = data.filter(r => { const h = _rowHour(r); return h === null || _isInPeriodWindow(h); }).length;
+    const windowNote = (SESSION_PERIOD_START_HOUR !== null && inWindowCount < data.length)
+        ? ` (${inWindowCount} in period window)`
+        : '';
     document.getElementById('row-count').textContent =
-        data.length > 500 ? `Showing 500 of ${data.length.toLocaleString()} rows` : `${data.length.toLocaleString()} rows`;
+        data.length > 500 ? `Showing 500 of ${data.length.toLocaleString()} rows${windowNote}` : `${data.length.toLocaleString()} rows${windowNote}`;
 
     // Search functionality
     document.getElementById('table-search').addEventListener('input', function(e) {
@@ -427,20 +472,7 @@ function renderTable(headers, data) {
         );
 
         const displayFiltered = filtered.slice(0, 500);
-        tbody.innerHTML = displayFiltered.map(row =>
-            '<tr class="hover:bg-gray-50 dark:hover:bg-gray-800/50">' +
-            headers.map(h => {
-                const val = row[h];
-                let displayVal = val;
-                if (val === null || val === undefined) {
-                    displayVal = '-';
-                } else if (typeof val === 'number') {
-                    displayVal = val.toFixed(1);
-                }
-                return `<td class="px-4 py-2 text-gray-700 dark:text-gray-300">${escapeHtml(String(displayVal))}</td>`;
-            }).join('') +
-            '</tr>'
-        ).join('');
+        tbody.innerHTML = displayFiltered.map(row => _buildRow(headers, row)).join('');
 
         document.getElementById('row-count').textContent =
             filtered.length > 500 ? `Showing 500 of ${filtered.length.toLocaleString()} filtered rows` : `${filtered.length.toLocaleString()} rows`;
diff --git a/templates/session_detail.html b/templates/session_detail.html
new file mode 100644
index 0000000..c3bece0
--- /dev/null
+++ b/templates/session_detail.html
@@ -0,0 +1,371 @@
+{% extends "base.html" %}
+
+{% block title %}{{ session.session_label or 'Session' }} — {{ project.name }}{% endblock %}
+
+{% block content %}
+<div class="max-w-5xl mx-auto">
+    <!-- Breadcrumb -->
+    <nav class="flex items-center space-x-2 text-sm text-gray-500 dark:text-gray-400 mb-4">
+        <a href="/projects" class="hover:text-seismo-orange">Projects</a>
+        <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"></path>
+        </svg>
+        <a href="/projects/{{ project_id }}" class="hover:text-seismo-orange">{{ project.name }}</a>
+        <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"></path>
+        </svg>
+        <span class="text-gray-900 dark:text-white truncate max-w-xs">{{ session.session_label or ('Session ' + session.id[:8] + '…') }}</span>
+    </nav>
+
+    <!-- Header -->
+    <div class="flex items-start justify-between gap-4 mb-6">
+        <div>
+            <h1 class="text-2xl font-bold text-gray-900 dark:text-white flex items-center gap-3">
+                <svg class="w-7 h-7 text-seismo-orange" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z"></path>
+                </svg>
+                <span id="header-label">{{ session.session_label or ('Session ' + session.id[:8] + '…') }}</span>
+            </h1>
+            {% if location %}
+            <p class="text-sm text-gray-500 dark:text-gray-400 mt-1">{{ location.name }}{% if unit %} · {{ unit.id }}{% endif %}</p>
+            {% endif %}
+        </div>
+        <div class="flex items-center gap-2 shrink-0">
+            {% if session.status == 'completed' %}
+            <span class="px-3 py-1 text-xs font-medium bg-green-100 text-green-800 dark:bg-green-900/30 dark:text-green-300 rounded-full">Completed</span>
+            {% elif session.status == 'recording' %}
+            <span class="px-3 py-1 text-xs font-medium bg-red-100 text-red-800 dark:bg-red-900/30 dark:text-red-300 rounded-full flex items-center gap-1">
+                <span class="w-2 h-2 bg-red-500 rounded-full animate-pulse"></span> Recording
+            </span>
+            {% endif %}
+        </div>
+    </div>
+
+    <div class="grid grid-cols-1 lg:grid-cols-3 gap-6">
+
+        <!-- LEFT COLUMN: Info + Edit -->
+        <div class="lg:col-span-1 space-y-4">
+
+            <!-- Session Info Card -->
+            <div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 p-5">
+                <h2 class="text-sm font-semibold text-gray-700 dark:text-gray-300 uppercase tracking-wide mb-3">Session Info</h2>
+                <dl class="space-y-2 text-sm">
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Label</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white text-right max-w-[180px] truncate"
+                            id="info-label">{{ session.session_label or '—' }}</dd>
+                    </div>
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Location</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white">{{ location.name if location else '—' }}</dd>
+                    </div>
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Period</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white" id="info-period">
+                            {% set PLABELS = {'weekday_day':'Weekday Day','weekday_night':'Weekday Night','weekend_day':'Weekend Day','weekend_night':'Weekend Night'} %}
+                            {{ PLABELS.get(session.period_type, '—') }}
+                        </dd>
+                    </div>
+                    {% if effective_range %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Effective</dt>
+                        <dd class="font-medium text-indigo-600 dark:text-indigo-400 text-right text-xs" id="info-effective">{{ effective_range }}</dd>
+                    </div>
+                    {% else %}
+                    <div class="flex justify-between hidden" id="info-effective-row">
+                        <dt class="text-gray-500 dark:text-gray-400">Effective</dt>
+                        <dd class="font-medium text-indigo-600 dark:text-indigo-400 text-right text-xs" id="info-effective"></dd>
+                    </div>
+                    {% endif %}
+                    {% if session.started_at %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Started</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white text-right">{{ session.started_at|local_datetime }}</dd>
+                    </div>
+                    {% endif %}
+                    {% if session.stopped_at %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Ended</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white text-right">{{ session.stopped_at|local_datetime }}</dd>
+                    </div>
+                    {% endif %}
+                    {% if session.duration_seconds %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Duration</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white">{{ session.duration_seconds // 3600 }}h {{ (session.duration_seconds % 3600) // 60 }}m</dd>
+                    </div>
+                    {% endif %}
+                    {% if session.device_model %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Device Model</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white">{{ session.device_model }}</dd>
+                    </div>
+                    {% endif %}
+                    {% if session_meta.get('store_name') %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Store Name</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white">{{ session_meta.store_name }}</dd>
+                    </div>
+                    {% endif %}
+                    {% if session_meta.get('serial_number') %}
+                    <div class="flex justify-between">
+                        <dt class="text-gray-500 dark:text-gray-400">Serial #</dt>
+                        <dd class="font-medium text-gray-900 dark:text-white">{{ session_meta.serial_number }}</dd>
+                    </div>
+                    {% endif %}
+                </dl>
+            </div>
+
+            <!-- Edit Card -->
+            <div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 p-5">
+                <h2 class="text-sm font-semibold text-gray-700 dark:text-gray-300 uppercase tracking-wide mb-3">Edit Session</h2>
+                <form id="edit-form" class="space-y-3" onsubmit="saveSession(event)">
+                    <div>
+                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">Label</label>
+                        <input type="text" id="edit-label" name="session_label"
+                               value="{{ session.session_label or '' }}"
+                               placeholder="e.g. NRL-1 — Mon 3/24 — Night"
+                               class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                    </div>
+                    <div>
+                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">Period Type</label>
+                        <select id="edit-period-type" name="period_type"
+                                class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                            <option value="">— Not Set —</option>
+                            <option value="weekday_day"   {% if session.period_type == 'weekday_day' %}selected{% endif %}>Weekday Day</option>
+                            <option value="weekday_night" {% if session.period_type == 'weekday_night' %}selected{% endif %}>Weekday Night</option>
+                            <option value="weekend_day"   {% if session.period_type == 'weekend_day' %}selected{% endif %}>Weekend Day</option>
+                            <option value="weekend_night" {% if session.period_type == 'weekend_night' %}selected{% endif %}>Weekend Night</option>
+                        </select>
+                    </div>
+                    <div class="grid grid-cols-2 gap-2">
+                        <div>
+                            <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">Start Hour (0–23)</label>
+                            <input type="number" min="0" max="23" id="edit-start-hour" name="period_start_hour"
+                                   value="{{ session.period_start_hour if session.period_start_hour is not none else '' }}"
+                                   placeholder="e.g. 19"
+                                   class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                        </div>
+                        <div>
+                            <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">End Hour (0–23)</label>
+                            <input type="number" min="0" max="23" id="edit-end-hour" name="period_end_hour"
+                                   value="{{ session.period_end_hour if session.period_end_hour is not none else '' }}"
+                                   placeholder="e.g. 7"
+                                   class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                        </div>
+                    </div>
+                    <div>
+                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">Start Time (local)</label>
+                        <input type="datetime-local" id="edit-started-at" name="started_at"
+                               value="{{ session.started_at|local_datetime_input if session.started_at else '' }}"
+                               class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                    </div>
+                    <div>
+                        <label class="block text-xs text-gray-500 dark:text-gray-400 mb-1">End Time (local)</label>
+                        <input type="datetime-local" id="edit-stopped-at" name="stopped_at"
+                               value="{{ session.stopped_at|local_datetime_input if session.stopped_at else '' }}"
+                               class="w-full text-sm bg-gray-50 dark:bg-slate-700 border border-gray-200 dark:border-gray-600 rounded-lg px-3 py-2 text-gray-900 dark:text-white focus:outline-none focus:border-seismo-orange">
+                    </div>
+                    <div class="flex gap-2 pt-1">
+                        <button type="submit"
+                                class="flex-1 text-sm py-2 bg-seismo-orange text-white rounded-lg hover:bg-orange-600 transition-colors font-medium">
+                            Save Changes
+                        </button>
+                        <button type="button" onclick="fillPeriodDefaults()"
+                                class="text-sm py-2 px-3 border border-gray-200 dark:border-gray-600 rounded-lg text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-slate-700 transition-colors"
+                                title="Fill default hours for selected period type">
+                            Defaults
+                        </button>
+                    </div>
+                    <div id="save-status" class="hidden text-xs text-center pt-1"></div>
+                </form>
+            </div>
+        </div>
+
+        <!-- RIGHT COLUMN: Files + Report Actions -->
+        <div class="lg:col-span-2 space-y-5">
+
+            <!-- Files List -->
+            <div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 overflow-hidden">
+                <div class="px-5 py-4 border-b border-gray-200 dark:border-gray-700 flex items-center justify-between">
+                    <h2 class="text-sm font-semibold text-gray-700 dark:text-gray-300 uppercase tracking-wide">
+                        Data Files
+                        <span class="ml-2 text-xs font-normal text-gray-400">({{ files|length }})</span>
+                    </h2>
+                </div>
+                {% if files %}
+                <div class="divide-y divide-gray-100 dark:divide-gray-700">
+                    {% for f in files %}
+                    {% set fname = f.file_path.split('/')[-1] %}
+                    {% set is_rnd = fname.lower().endswith('.rnd') %}
+                    {% set is_leq = '_leq_' in fname.lower() or fname.lower().startswith('au2_') %}
+                    <div class="flex items-center gap-3 px-5 py-3 hover:bg-gray-50 dark:hover:bg-slate-700/50 transition-colors">
+                        <!-- Icon -->
+                        <div class="shrink-0 w-8 h-8 rounded-lg flex items-center justify-center
+                                    {% if is_rnd %}bg-green-100 dark:bg-green-900/30{% else %}bg-gray-100 dark:bg-gray-700{% endif %}">
+                            {% if is_rnd %}
+                            <svg class="w-4 h-4 text-green-600 dark:text-green-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z"></path>
+                            </svg>
+                            {% else %}
+                            <svg class="w-4 h-4 text-gray-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path>
+                            </svg>
+                            {% endif %}
+                        </div>
+
+                        <!-- Name + meta -->
+                        <div class="min-w-0 flex-1">
+                            <div class="text-sm font-medium text-gray-900 dark:text-white truncate">{{ fname }}</div>
+                            <div class="text-xs text-gray-400 flex items-center gap-2 mt-0.5">
+                                <span>{{ f.file_type | upper }}</span>
+                                {% if f.file_size_bytes %}
+                                <span>{{ (f.file_size_bytes / 1024) | round(1) }} KB</span>
+                                {% endif %}
+                                {% if is_leq %}<span class="text-green-600 dark:text-green-400 font-medium">Leq</span>{% endif %}
+                            </div>
+                        </div>
+
+                        <!-- Actions -->
+                        <div class="flex items-center gap-2 shrink-0">
+                            {% if is_rnd %}
+                            <a href="/api/projects/{{ project_id }}/files/{{ f.id }}/view-rnd"
+                               class="px-2 py-1 text-xs bg-green-600 text-white rounded hover:bg-green-700 transition-colors">
+                                View
+                            </a>
+                            {% if is_leq %}
+                            <button onclick="openSingleFileReport('{{ f.id }}', '{{ fname }}')"
+                                    class="px-2 py-1 text-xs bg-emerald-600 text-white rounded hover:bg-emerald-700 transition-colors">
+                                Report
+                            </button>
+                            {% endif %}
+                            {% endif %}
+                            <a href="/api/projects/{{ project_id }}/files/{{ f.id }}/download"
+                               class="px-2 py-1 text-xs border border-gray-200 dark:border-gray-600 text-gray-600 dark:text-gray-400 rounded hover:bg-gray-100 dark:hover:bg-slate-600 transition-colors">
+                                Download
+                            </a>
+                        </div>
+                    </div>
+                    {% endfor %}
+                </div>
+                {% else %}
+                <div class="px-5 py-10 text-center text-gray-400">
+                    <p>No files found for this session.</p>
+                </div>
+                {% endif %}
+            </div>
+
+            <!-- Report Actions -->
+            <div class="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-gray-700 p-5">
+                <h2 class="text-sm font-semibold text-gray-700 dark:text-gray-300 uppercase tracking-wide mb-3">Report Actions</h2>
+
+                {% if session.status == 'completed' %}
+                {% set has_rnd = files | selectattr('file_type', 'equalto', 'rnd') | list | length > 0 %}
+                {% if has_rnd %}
+                <div class="p-3 bg-gray-50 dark:bg-slate-700/50 rounded-lg space-y-2">
+                    <p class="text-xs text-gray-600 dark:text-gray-400">
+                        Use the <strong>Combined Report Wizard</strong> to generate an Excel report for this session, or click <strong>View</strong> on a Leq file above to access per-file reporting.
+                        {% if session.period_start_hour is not none %}
+                        <br><span class="text-indigo-600 dark:text-indigo-400">Period window {{ session.period_start_hour }}:00–{{ session.period_end_hour }}:00 will be applied.</span>
+                        {% endif %}
+                    </p>
+                    <a href="/projects/{{ project_id }}?tab=data"
+                       class="inline-flex items-center gap-2 px-4 py-2 bg-emerald-600 text-white text-sm rounded-lg hover:bg-emerald-700 transition-colors font-medium">
+                        <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 17v-2m3 2v-4m3 4v-6m2 10H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z"></path>
+                        </svg>
+                        Go to Combined Report Wizard
+                    </a>
+                </div>
+                {% else %}
+                <p class="text-sm text-gray-400 dark:text-gray-500">No .rnd files found — upload data to generate a report.</p>
+                {% endif %}
+                {% else %}
+                <p class="text-sm text-gray-400 dark:text-gray-500">Reports are available after the session is completed.</p>
+                {% endif %}
+            </div>
+
+        </div>
+    </div>
+</div>
+
+<script>
+const PROJECT_ID = '{{ project_id }}';
+const SESSION_ID = '{{ session.id }}';
+
+const PERIOD_DEFAULT_HOURS = {
+    weekday_day:   {start: 7,  end: 19},
+    weekday_night: {start: 19, end: 7},
+    weekend_day:   {start: 7,  end: 19},
+    weekend_night: {start: 19, end: 7},
+};
+
+function fillPeriodDefaults() {
+    const pt = document.getElementById('edit-period-type').value;
+    const defaults = PERIOD_DEFAULT_HOURS[pt];
+    if (defaults) {
+        document.getElementById('edit-start-hour').value = defaults.start;
+        document.getElementById('edit-end-hour').value   = defaults.end;
+    }
+}
+
+async function saveSession(e) {
+    e.preventDefault();
+    const status = document.getElementById('save-status');
+    status.className = 'text-xs text-center pt-1 text-gray-400';
+    status.textContent = 'Saving…';
+    status.classList.remove('hidden');
+
+    const form = document.getElementById('edit-form');
+    const payload = {};
+
+    const label = form.session_label.value.trim();
+    payload.session_label = label || null;
+
+    const pt = form.period_type.value;
+    payload.period_type = pt || null;
+
+    const sh = form.period_start_hour.value;
+    const eh = form.period_end_hour.value;
+    payload.period_start_hour = sh !== '' ? parseInt(sh, 10) : null;
+    payload.period_end_hour   = eh !== '' ? parseInt(eh, 10) : null;
+
+    const sa = form.started_at.value;
+    if (sa) payload.started_at = sa;
+
+    const st = form.stopped_at.value;
+    if (st) payload.stopped_at = st;
+    else if (form.stopped_at.value === '') payload.stopped_at = null;
+
+    try {
+        const resp = await fetch(`/api/projects/${PROJECT_ID}/sessions/${SESSION_ID}`, {
+            method: 'PATCH',
+            headers: {'Content-Type': 'application/json'},
+            body: JSON.stringify(payload),
+        });
+        if (!resp.ok) throw new Error(await resp.text());
+        const result = await resp.json();
+
+        // Update displayed label
+        const newLabel = result.session_label || ('Session ' + SESSION_ID.slice(0, 8) + '…');
+        document.getElementById('header-label').textContent = newLabel;
+        document.getElementById('info-label').textContent = result.session_label || '—';
+        document.getElementById('info-period').textContent = {
+            weekday_day: 'Weekday Day', weekday_night: 'Weekday Night',
+            weekend_day: 'Weekend Day', weekend_night: 'Weekend Night'
+        }[result.period_type] || '—';
+
+        status.className = 'text-xs text-center pt-1 text-green-600 dark:text-green-400';
+        status.textContent = 'Saved!';
+        setTimeout(() => status.classList.add('hidden'), 2500);
+    } catch(err) {
+        status.className = 'text-xs text-center pt-1 text-red-500';
+        status.textContent = 'Error: ' + err.message;
+    }
+}
+
+function openSingleFileReport(fileId, filename) {
+    window.location.href = `/api/projects/${PROJECT_ID}/files/${fileId}/view-rnd`;
+}
+</script>
+{% endblock %}