add: Calander and reservation mode implemented.

backend/main.py

@@ -115,6 +115,10 @@ app.include_router(alerts.router)
 from backend.routers import recurring_schedules
 app.include_router(recurring_schedules.router)
 
+# Fleet Calendar router
+from backend.routers import fleet_calendar
+app.include_router(fleet_calendar.router)
+
 # Start scheduler service and device status monitor on application startup
 from backend.services.scheduler import start_scheduler, stop_scheduler
 from backend.services.device_status_monitor import start_device_status_monitor, stop_device_status_monitor

backend/migrate_add_job_reservations.py

@@ -0,0 +1,103 @@
+"""
+Migration script to add job reservations for the Fleet Calendar feature.
+
+This creates two tables:
+- job_reservations: Track future unit assignments for jobs/projects
+- job_reservation_units: Link specific units to reservations
+
+Run this script once to migrate an existing database.
+"""
+
+import sqlite3
+import os
+
+# Database path
+DB_PATH = "./data/seismo_fleet.db"
+
+
+def migrate_database():
+    """Create the job_reservations and job_reservation_units tables"""
+
+    if not os.path.exists(DB_PATH):
+        print(f"Database not found at {DB_PATH}")
+        print("The database will be created automatically when you run the application.")
+        return
+
+    print(f"Migrating database: {DB_PATH}")
+
+    conn = sqlite3.connect(DB_PATH)
+    cursor = conn.cursor()
+
+    # Check if job_reservations table already exists
+    cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='job_reservations'")
+    if cursor.fetchone():
+        print("Migration already applied - job_reservations table exists")
+        conn.close()
+        return
+
+    print("Creating job_reservations table...")
+
+    try:
+        # Create job_reservations table
+        cursor.execute("""
+            CREATE TABLE job_reservations (
+                id TEXT PRIMARY KEY,
+                name TEXT NOT NULL,
+                project_id TEXT,
+                start_date DATE NOT NULL,
+                end_date DATE NOT NULL,
+                assignment_type TEXT NOT NULL DEFAULT 'quantity',
+                device_type TEXT DEFAULT 'seismograph',
+                quantity_needed INTEGER,
+                notes TEXT,
+                color TEXT DEFAULT '#3B82F6',
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+            )
+        """)
+        print("  Created job_reservations table")
+
+        # Create indexes for job_reservations
+        cursor.execute("CREATE INDEX idx_job_reservations_project_id ON job_reservations(project_id)")
+        print("  Created index on project_id")
+
+        cursor.execute("CREATE INDEX idx_job_reservations_dates ON job_reservations(start_date, end_date)")
+        print("  Created index on dates")
+
+        # Create job_reservation_units table
+        print("Creating job_reservation_units table...")
+        cursor.execute("""
+            CREATE TABLE job_reservation_units (
+                id TEXT PRIMARY KEY,
+                reservation_id TEXT NOT NULL,
+                unit_id TEXT NOT NULL,
+                assignment_source TEXT DEFAULT 'specific',
+                assigned_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                FOREIGN KEY (reservation_id) REFERENCES job_reservations(id),
+                FOREIGN KEY (unit_id) REFERENCES roster(id)
+            )
+        """)
+        print("  Created job_reservation_units table")
+
+        # Create indexes for job_reservation_units
+        cursor.execute("CREATE INDEX idx_job_reservation_units_reservation_id ON job_reservation_units(reservation_id)")
+        print("  Created index on reservation_id")
+
+        cursor.execute("CREATE INDEX idx_job_reservation_units_unit_id ON job_reservation_units(unit_id)")
+        print("  Created index on unit_id")
+
+        conn.commit()
+        print("\nMigration completed successfully!")
+        print("You can now use the Fleet Calendar to manage unit reservations.")
+
+    except sqlite3.Error as e:
+        print(f"\nError during migration: {e}")
+        conn.rollback()
+        raise
+
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    migrate_database()

backend/migrate_add_tbd_dates.py

@@ -0,0 +1,89 @@
+"""
+Migration: Add TBD date support to job reservations
+
+Adds columns:
+- job_reservations.estimated_end_date: For planning when end is TBD
+- job_reservations.end_date_tbd: Boolean flag for TBD end dates
+- job_reservation_units.unit_start_date: Unit-specific start (for swaps)
+- job_reservation_units.unit_end_date: Unit-specific end (for swaps)
+- job_reservation_units.unit_end_tbd: Unit-specific TBD flag
+- job_reservation_units.notes: Notes for the assignment
+
+Also makes job_reservations.end_date nullable.
+"""
+
+import sqlite3
+import sys
+from pathlib import Path
+
+def migrate(db_path: str):
+    """Run the migration."""
+    print(f"Migrating database: {db_path}")
+
+    conn = sqlite3.connect(db_path)
+    cursor = conn.cursor()
+
+    try:
+        # Check if job_reservations table exists
+        cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='job_reservations'")
+        if not cursor.fetchone():
+            print("job_reservations table does not exist. Skipping migration.")
+            return
+
+        # Get existing columns in job_reservations
+        cursor.execute("PRAGMA table_info(job_reservations)")
+        existing_cols = {row[1] for row in cursor.fetchall()}
+
+        # Add new columns to job_reservations if they don't exist
+        if 'estimated_end_date' not in existing_cols:
+            print("Adding estimated_end_date column to job_reservations...")
+            cursor.execute("ALTER TABLE job_reservations ADD COLUMN estimated_end_date DATE")
+
+        if 'end_date_tbd' not in existing_cols:
+            print("Adding end_date_tbd column to job_reservations...")
+            cursor.execute("ALTER TABLE job_reservations ADD COLUMN end_date_tbd BOOLEAN DEFAULT 0")
+
+        # Get existing columns in job_reservation_units
+        cursor.execute("PRAGMA table_info(job_reservation_units)")
+        unit_cols = {row[1] for row in cursor.fetchall()}
+
+        # Add new columns to job_reservation_units if they don't exist
+        if 'unit_start_date' not in unit_cols:
+            print("Adding unit_start_date column to job_reservation_units...")
+            cursor.execute("ALTER TABLE job_reservation_units ADD COLUMN unit_start_date DATE")
+
+        if 'unit_end_date' not in unit_cols:
+            print("Adding unit_end_date column to job_reservation_units...")
+            cursor.execute("ALTER TABLE job_reservation_units ADD COLUMN unit_end_date DATE")
+
+        if 'unit_end_tbd' not in unit_cols:
+            print("Adding unit_end_tbd column to job_reservation_units...")
+            cursor.execute("ALTER TABLE job_reservation_units ADD COLUMN unit_end_tbd BOOLEAN DEFAULT 0")
+
+        if 'notes' not in unit_cols:
+            print("Adding notes column to job_reservation_units...")
+            cursor.execute("ALTER TABLE job_reservation_units ADD COLUMN notes TEXT")
+
+        conn.commit()
+        print("Migration completed successfully!")
+
+    except Exception as e:
+        print(f"Migration failed: {e}")
+        conn.rollback()
+        raise
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    # Default to dev database
+    db_path = "./data-dev/seismo_fleet.db"
+
+    if len(sys.argv) > 1:
+        db_path = sys.argv[1]
+
+    if not Path(db_path).exists():
+        print(f"Database not found: {db_path}")
+        sys.exit(1)
+
+    migrate(db_path)

backend/migrate_fix_end_date_nullable.py

@@ -0,0 +1,105 @@
+"""
+Migration: Make job_reservations.end_date nullable for TBD support
+
+SQLite doesn't support ALTER COLUMN, so we need to:
+1. Create a new table with the correct schema
+2. Copy data
+3. Drop old table
+4. Rename new table
+"""
+
+import sqlite3
+import sys
+from pathlib import Path
+
+def migrate(db_path: str):
+    """Run the migration."""
+    print(f"Migrating database: {db_path}")
+
+    conn = sqlite3.connect(db_path)
+    cursor = conn.cursor()
+
+    try:
+        # Check if job_reservations table exists
+        cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='job_reservations'")
+        if not cursor.fetchone():
+            print("job_reservations table does not exist. Skipping migration.")
+            return
+
+        # Check current schema
+        cursor.execute("PRAGMA table_info(job_reservations)")
+        columns = cursor.fetchall()
+        col_info = {row[1]: row for row in columns}
+
+        # Check if end_date is already nullable (notnull=0)
+        if 'end_date' in col_info and col_info['end_date'][3] == 0:
+            print("end_date is already nullable. Skipping table recreation.")
+            return
+
+        print("Recreating job_reservations table with nullable end_date...")
+
+        # Create new table with correct schema
+        cursor.execute("""
+            CREATE TABLE job_reservations_new (
+                id TEXT PRIMARY KEY,
+                name TEXT NOT NULL,
+                project_id TEXT,
+                start_date DATE NOT NULL,
+                end_date DATE,
+                estimated_end_date DATE,
+                end_date_tbd BOOLEAN DEFAULT 0,
+                assignment_type TEXT NOT NULL DEFAULT 'quantity',
+                device_type TEXT DEFAULT 'seismograph',
+                quantity_needed INTEGER,
+                notes TEXT,
+                color TEXT DEFAULT '#3B82F6',
+                created_at DATETIME,
+                updated_at DATETIME
+            )
+        """)
+
+        # Copy existing data
+        cursor.execute("""
+            INSERT INTO job_reservations_new
+            SELECT
+                id, name, project_id, start_date, end_date,
+                COALESCE(estimated_end_date, NULL) as estimated_end_date,
+                COALESCE(end_date_tbd, 0) as end_date_tbd,
+                assignment_type, device_type, quantity_needed, notes, color,
+                created_at, updated_at
+            FROM job_reservations
+        """)
+
+        # Drop old table
+        cursor.execute("DROP TABLE job_reservations")
+
+        # Rename new table
+        cursor.execute("ALTER TABLE job_reservations_new RENAME TO job_reservations")
+
+        # Recreate index
+        cursor.execute("CREATE INDEX IF NOT EXISTS ix_job_reservations_id ON job_reservations (id)")
+        cursor.execute("CREATE INDEX IF NOT EXISTS ix_job_reservations_project_id ON job_reservations (project_id)")
+
+        conn.commit()
+        print("Migration completed successfully!")
+
+    except Exception as e:
+        print(f"Migration failed: {e}")
+        conn.rollback()
+        raise
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    # Default to dev database
+    db_path = "./data-dev/seismo_fleet.db"
+
+    if len(sys.argv) > 1:
+        db_path = sys.argv[1]
+
+    if not Path(db_path).exists():
+        print(f"Database not found: {db_path}")
+        sys.exit(1)
+
+    migrate(db_path)

backend/models.py

@@ -402,3 +402,72 @@ class Alert(Base):
 
     created_at = Column(DateTime, default=datetime.utcnow)
     expires_at = Column(DateTime, nullable=True)  # Auto-dismiss after this time
+
+
+# ============================================================================
+# Fleet Calendar & Job Reservations
+# ============================================================================
+
+class JobReservation(Base):
+    """
+    Job reservations: reserve units for future jobs/projects.
+
+    Supports two assignment modes:
+    - "specific": Pick exact units (SN-001, SN-002, etc.)
+    - "quantity": Reserve a number of units (e.g., "need 8 seismographs")
+
+    Used by the Fleet Calendar to visualize unit availability over time.
+    """
+    __tablename__ = "job_reservations"
+
+    id = Column(String, primary_key=True, index=True)  # UUID
+    name = Column(String, nullable=False)  # "Job A - March deployment"
+    project_id = Column(String, nullable=True, index=True)  # Optional FK to Project
+
+    # Date range for the reservation
+    start_date = Column(Date, nullable=False)
+    end_date = Column(Date, nullable=True)  # Nullable = TBD / ongoing
+    estimated_end_date = Column(Date, nullable=True)  # For planning when end is TBD
+    end_date_tbd = Column(Boolean, default=False)  # True = end date unknown
+
+    # Assignment type: "specific" or "quantity"
+    assignment_type = Column(String, nullable=False, default="quantity")
+
+    # For quantity reservations
+    device_type = Column(String, default="seismograph")  # seismograph | slm
+    quantity_needed = Column(Integer, nullable=True)  # e.g., 8 units
+
+    # Metadata
+    notes = Column(Text, nullable=True)
+    color = Column(String, default="#3B82F6")  # For calendar display (blue default)
+
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+
+class JobReservationUnit(Base):
+    """
+    Links specific units to job reservations.
+
+    Used when:
+    - assignment_type="specific": Units are directly assigned
+    - assignment_type="quantity": Units can be filled in later
+
+    Supports unit swaps: same reservation can have multiple units with
+    different date ranges (e.g., BE17353 Feb-Jun, then BE18438 Jun-Nov).
+    """
+    __tablename__ = "job_reservation_units"
+
+    id = Column(String, primary_key=True, index=True)  # UUID
+    reservation_id = Column(String, nullable=False, index=True)  # FK to JobReservation
+    unit_id = Column(String, nullable=False, index=True)  # FK to RosterUnit
+
+    # Unit-specific date range (for swaps) - defaults to reservation dates if null
+    unit_start_date = Column(Date, nullable=True)  # When this specific unit starts
+    unit_end_date = Column(Date, nullable=True)  # When this unit ends (swap out date)
+    unit_end_tbd = Column(Boolean, default=False)  # True = end unknown (until cal expires or job ends)
+
+    # Track how this assignment was made
+    assignment_source = Column(String, default="specific")  # "specific" | "filled" | "swap"
+    assigned_at = Column(DateTime, default=datetime.utcnow)
+    notes = Column(Text, nullable=True)  # "Replacing BE17353" etc.

backend/routers/fleet_calendar.py

@@ -0,0 +1,610 @@
+"""
+Fleet Calendar Router
+
+API endpoints for the Fleet Calendar feature:
+- Calendar page and data
+- Job reservation CRUD
+- Unit assignment management
+- Availability checking
+"""
+
+from fastapi import APIRouter, Request, Depends, HTTPException, Query
+from fastapi.responses import HTMLResponse, JSONResponse
+from sqlalchemy.orm import Session
+from datetime import datetime, date, timedelta
+from typing import Optional, List
+import uuid
+import logging
+
+from backend.database import get_db
+from backend.models import (
+    RosterUnit, JobReservation, JobReservationUnit,
+    UserPreferences, Project
+)
+from backend.templates_config import templates
+from backend.services.fleet_calendar_service import (
+    get_day_summary,
+    get_calendar_year_data,
+    get_rolling_calendar_data,
+    check_calibration_conflicts,
+    get_available_units_for_period,
+    get_calibration_status
+)
+
+router = APIRouter(tags=["fleet-calendar"])
+logger = logging.getLogger(__name__)
+
+
+# ============================================================================
+# Calendar Page
+# ============================================================================
+
+@router.get("/fleet-calendar", response_class=HTMLResponse)
+async def fleet_calendar_page(
+    request: Request,
+    year: Optional[int] = None,
+    month: Optional[int] = None,
+    device_type: str = "seismograph",
+    db: Session = Depends(get_db)
+):
+    """Main Fleet Calendar page with rolling 12-month view."""
+    today = date.today()
+
+    # Default to current month as the start
+    if year is None:
+        year = today.year
+    if month is None:
+        month = today.month
+
+    # Get calendar data for 12 months starting from year/month
+    calendar_data = get_rolling_calendar_data(db, year, month, device_type)
+
+    # Get projects for the reservation form dropdown
+    projects = db.query(Project).filter(
+        Project.status == "active"
+    ).order_by(Project.name).all()
+
+    # Calculate prev/next month navigation
+    prev_year, prev_month = (year - 1, 12) if month == 1 else (year, month - 1)
+    next_year, next_month = (year + 1, 1) if month == 12 else (year, month + 1)
+
+    return templates.TemplateResponse(
+        "fleet_calendar.html",
+        {
+            "request": request,
+            "start_year": year,
+            "start_month": month,
+            "prev_year": prev_year,
+            "prev_month": prev_month,
+            "next_year": next_year,
+            "next_month": next_month,
+            "device_type": device_type,
+            "calendar_data": calendar_data,
+            "projects": projects,
+            "today": today.isoformat()
+        }
+    )
+
+
+# ============================================================================
+# Calendar Data API
+# ============================================================================
+
+@router.get("/api/fleet-calendar/data", response_class=JSONResponse)
+async def get_calendar_data(
+    year: int,
+    device_type: str = "seismograph",
+    db: Session = Depends(get_db)
+):
+    """Get calendar data for a specific year."""
+    return get_calendar_year_data(db, year, device_type)
+
+
+@router.get("/api/fleet-calendar/day/{date_str}", response_class=HTMLResponse)
+async def get_day_detail(
+    request: Request,
+    date_str: str,
+    device_type: str = "seismograph",
+    db: Session = Depends(get_db)
+):
+    """Get detailed view for a specific day (HTMX partial)."""
+    try:
+        check_date = date.fromisoformat(date_str)
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid date format. Use YYYY-MM-DD")
+
+    day_data = get_day_summary(db, check_date, device_type)
+
+    # Get projects for display names
+    projects = {p.id: p for p in db.query(Project).all()}
+
+    return templates.TemplateResponse(
+        "partials/fleet_calendar/day_detail.html",
+        {
+            "request": request,
+            "day_data": day_data,
+            "date_str": date_str,
+            "date_display": check_date.strftime("%B %d, %Y"),
+            "device_type": device_type,
+            "projects": projects
+        }
+    )
+
+
+# ============================================================================
+# Reservation CRUD
+# ============================================================================
+
+@router.post("/api/fleet-calendar/reservations", response_class=JSONResponse)
+async def create_reservation(
+    request: Request,
+    db: Session = Depends(get_db)
+):
+    """Create a new job reservation."""
+    data = await request.json()
+
+    # Validate required fields
+    required = ["name", "start_date", "assignment_type"]
+    for field in required:
+        if field not in data:
+            raise HTTPException(status_code=400, detail=f"Missing required field: {field}")
+
+    # Need either end_date or end_date_tbd
+    end_date_tbd = data.get("end_date_tbd", False)
+    if not end_date_tbd and not data.get("end_date"):
+        raise HTTPException(status_code=400, detail="End date is required unless marked as TBD")
+
+    try:
+        start_date = date.fromisoformat(data["start_date"])
+        end_date = date.fromisoformat(data["end_date"]) if data.get("end_date") else None
+        estimated_end_date = date.fromisoformat(data["estimated_end_date"]) if data.get("estimated_end_date") else None
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid date format. Use YYYY-MM-DD")
+
+    if end_date and end_date < start_date:
+        raise HTTPException(status_code=400, detail="End date must be after start date")
+
+    if estimated_end_date and estimated_end_date < start_date:
+        raise HTTPException(status_code=400, detail="Estimated end date must be after start date")
+
+    reservation = JobReservation(
+        id=str(uuid.uuid4()),
+        name=data["name"],
+        project_id=data.get("project_id"),
+        start_date=start_date,
+        end_date=end_date,
+        estimated_end_date=estimated_end_date,
+        end_date_tbd=end_date_tbd,
+        assignment_type=data["assignment_type"],
+        device_type=data.get("device_type", "seismograph"),
+        quantity_needed=data.get("quantity_needed"),
+        notes=data.get("notes"),
+        color=data.get("color", "#3B82F6")
+    )
+
+    db.add(reservation)
+
+    # If specific units were provided, assign them
+    if data.get("unit_ids") and data["assignment_type"] == "specific":
+        for unit_id in data["unit_ids"]:
+            assignment = JobReservationUnit(
+                id=str(uuid.uuid4()),
+                reservation_id=reservation.id,
+                unit_id=unit_id,
+                assignment_source="specific"
+            )
+            db.add(assignment)
+
+    db.commit()
+
+    logger.info(f"Created reservation: {reservation.name} ({reservation.id})")
+
+    return {
+        "success": True,
+        "reservation_id": reservation.id,
+        "message": f"Created reservation: {reservation.name}"
+    }
+
+
+@router.get("/api/fleet-calendar/reservations/{reservation_id}", response_class=JSONResponse)
+async def get_reservation(
+    reservation_id: str,
+    db: Session = Depends(get_db)
+):
+    """Get a specific reservation with its assigned units."""
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        raise HTTPException(status_code=404, detail="Reservation not found")
+
+    # Get assigned units
+    assignments = db.query(JobReservationUnit).filter_by(
+        reservation_id=reservation_id
+    ).all()
+
+    unit_ids = [a.unit_id for a in assignments]
+    units = db.query(RosterUnit).filter(RosterUnit.id.in_(unit_ids)).all() if unit_ids else []
+
+    return {
+        "id": reservation.id,
+        "name": reservation.name,
+        "project_id": reservation.project_id,
+        "start_date": reservation.start_date.isoformat(),
+        "end_date": reservation.end_date.isoformat() if reservation.end_date else None,
+        "estimated_end_date": reservation.estimated_end_date.isoformat() if reservation.estimated_end_date else None,
+        "end_date_tbd": reservation.end_date_tbd,
+        "assignment_type": reservation.assignment_type,
+        "device_type": reservation.device_type,
+        "quantity_needed": reservation.quantity_needed,
+        "notes": reservation.notes,
+        "color": reservation.color,
+        "assigned_units": [
+            {
+                "id": u.id,
+                "last_calibrated": u.last_calibrated.isoformat() if u.last_calibrated else None,
+                "deployed": u.deployed
+            }
+            for u in units
+        ]
+    }
+
+
+@router.put("/api/fleet-calendar/reservations/{reservation_id}", response_class=JSONResponse)
+async def update_reservation(
+    reservation_id: str,
+    request: Request,
+    db: Session = Depends(get_db)
+):
+    """Update an existing reservation."""
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        raise HTTPException(status_code=404, detail="Reservation not found")
+
+    data = await request.json()
+
+    # Update fields if provided
+    if "name" in data:
+        reservation.name = data["name"]
+    if "project_id" in data:
+        reservation.project_id = data["project_id"]
+    if "start_date" in data:
+        reservation.start_date = date.fromisoformat(data["start_date"])
+    if "end_date" in data:
+        reservation.end_date = date.fromisoformat(data["end_date"]) if data["end_date"] else None
+    if "estimated_end_date" in data:
+        reservation.estimated_end_date = date.fromisoformat(data["estimated_end_date"]) if data["estimated_end_date"] else None
+    if "end_date_tbd" in data:
+        reservation.end_date_tbd = data["end_date_tbd"]
+    if "assignment_type" in data:
+        reservation.assignment_type = data["assignment_type"]
+    if "quantity_needed" in data:
+        reservation.quantity_needed = data["quantity_needed"]
+    if "notes" in data:
+        reservation.notes = data["notes"]
+    if "color" in data:
+        reservation.color = data["color"]
+
+    reservation.updated_at = datetime.utcnow()
+
+    db.commit()
+
+    logger.info(f"Updated reservation: {reservation.name} ({reservation.id})")
+
+    return {
+        "success": True,
+        "message": f"Updated reservation: {reservation.name}"
+    }
+
+
+@router.delete("/api/fleet-calendar/reservations/{reservation_id}", response_class=JSONResponse)
+async def delete_reservation(
+    reservation_id: str,
+    db: Session = Depends(get_db)
+):
+    """Delete a reservation and its unit assignments."""
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        raise HTTPException(status_code=404, detail="Reservation not found")
+
+    # Delete unit assignments first
+    db.query(JobReservationUnit).filter_by(reservation_id=reservation_id).delete()
+
+    # Delete the reservation
+    db.delete(reservation)
+    db.commit()
+
+    logger.info(f"Deleted reservation: {reservation.name} ({reservation_id})")
+
+    return {
+        "success": True,
+        "message": "Reservation deleted"
+    }
+
+
+# ============================================================================
+# Unit Assignment
+# ============================================================================
+
+@router.post("/api/fleet-calendar/reservations/{reservation_id}/assign-units", response_class=JSONResponse)
+async def assign_units_to_reservation(
+    reservation_id: str,
+    request: Request,
+    db: Session = Depends(get_db)
+):
+    """Assign specific units to a reservation."""
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        raise HTTPException(status_code=404, detail="Reservation not found")
+
+    data = await request.json()
+    unit_ids = data.get("unit_ids", [])
+
+    if not unit_ids:
+        raise HTTPException(status_code=400, detail="No units specified")
+
+    # Verify units exist
+    units = db.query(RosterUnit).filter(RosterUnit.id.in_(unit_ids)).all()
+    found_ids = {u.id for u in units}
+    missing = set(unit_ids) - found_ids
+    if missing:
+        raise HTTPException(status_code=404, detail=f"Units not found: {', '.join(missing)}")
+
+    # Check for conflicts (already assigned to overlapping reservations)
+    conflicts = []
+    for unit_id in unit_ids:
+        # Check if unit is already assigned to this reservation
+        existing = db.query(JobReservationUnit).filter_by(
+            reservation_id=reservation_id,
+            unit_id=unit_id
+        ).first()
+        if existing:
+            continue  # Already assigned, skip
+
+        # Check overlapping reservations
+        overlapping = db.query(JobReservation).join(
+            JobReservationUnit, JobReservation.id == JobReservationUnit.reservation_id
+        ).filter(
+            JobReservationUnit.unit_id == unit_id,
+            JobReservation.id != reservation_id,
+            JobReservation.start_date <= reservation.end_date,
+            JobReservation.end_date >= reservation.start_date
+        ).first()
+
+        if overlapping:
+            conflicts.append({
+                "unit_id": unit_id,
+                "conflict_reservation": overlapping.name,
+                "conflict_dates": f"{overlapping.start_date} - {overlapping.end_date}"
+            })
+            continue
+
+        # Add assignment
+        assignment = JobReservationUnit(
+            id=str(uuid.uuid4()),
+            reservation_id=reservation_id,
+            unit_id=unit_id,
+            assignment_source="filled" if reservation.assignment_type == "quantity" else "specific"
+        )
+        db.add(assignment)
+
+    db.commit()
+
+    # Check for calibration conflicts
+    cal_conflicts = check_calibration_conflicts(db, reservation_id)
+
+    assigned_count = db.query(JobReservationUnit).filter_by(
+        reservation_id=reservation_id
+    ).count()
+
+    return {
+        "success": True,
+        "assigned_count": assigned_count,
+        "conflicts": conflicts,
+        "calibration_warnings": cal_conflicts,
+        "message": f"Assigned {len(unit_ids) - len(conflicts)} units"
+    }
+
+
+@router.delete("/api/fleet-calendar/reservations/{reservation_id}/units/{unit_id}", response_class=JSONResponse)
+async def remove_unit_from_reservation(
+    reservation_id: str,
+    unit_id: str,
+    db: Session = Depends(get_db)
+):
+    """Remove a unit from a reservation."""
+    assignment = db.query(JobReservationUnit).filter_by(
+        reservation_id=reservation_id,
+        unit_id=unit_id
+    ).first()
+
+    if not assignment:
+        raise HTTPException(status_code=404, detail="Unit assignment not found")
+
+    db.delete(assignment)
+    db.commit()
+
+    return {
+        "success": True,
+        "message": f"Removed {unit_id} from reservation"
+    }
+
+
+# ============================================================================
+# Availability & Conflicts
+# ============================================================================
+
+@router.get("/api/fleet-calendar/availability", response_class=JSONResponse)
+async def check_availability(
+    start_date: str,
+    end_date: str,
+    device_type: str = "seismograph",
+    exclude_reservation_id: Optional[str] = None,
+    db: Session = Depends(get_db)
+):
+    """Get units available for a specific date range."""
+    try:
+        start = date.fromisoformat(start_date)
+        end = date.fromisoformat(end_date)
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid date format. Use YYYY-MM-DD")
+
+    available = get_available_units_for_period(
+        db, start, end, device_type, exclude_reservation_id
+    )
+
+    return {
+        "start_date": start_date,
+        "end_date": end_date,
+        "device_type": device_type,
+        "available_units": available,
+        "count": len(available)
+    }
+
+
+@router.get("/api/fleet-calendar/reservations/{reservation_id}/conflicts", response_class=JSONResponse)
+async def get_reservation_conflicts(
+    reservation_id: str,
+    db: Session = Depends(get_db)
+):
+    """Check for calibration conflicts in a reservation."""
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        raise HTTPException(status_code=404, detail="Reservation not found")
+
+    conflicts = check_calibration_conflicts(db, reservation_id)
+
+    return {
+        "reservation_id": reservation_id,
+        "reservation_name": reservation.name,
+        "conflicts": conflicts,
+        "has_conflicts": len(conflicts) > 0
+    }
+
+
+# ============================================================================
+# HTMX Partials
+# ============================================================================
+
+@router.get("/api/fleet-calendar/reservations-list", response_class=HTMLResponse)
+async def get_reservations_list(
+    request: Request,
+    year: Optional[int] = None,
+    month: Optional[int] = None,
+    device_type: str = "seismograph",
+    db: Session = Depends(get_db)
+):
+    """Get list of reservations as HTMX partial."""
+    from sqlalchemy import or_
+
+    today = date.today()
+    if year is None:
+        year = today.year
+    if month is None:
+        month = today.month
+
+    # Calculate 12-month window
+    start_date = date(year, month, 1)
+    # End date is 12 months later
+    end_year = year + ((month + 10) // 12)
+    end_month = ((month + 10) % 12) + 1
+    if end_month == 12:
+        end_date = date(end_year, 12, 31)
+    else:
+        end_date = date(end_year, end_month + 1, 1) - timedelta(days=1)
+
+    # Include TBD reservations that started before window end
+    reservations = db.query(JobReservation).filter(
+        JobReservation.device_type == device_type,
+        JobReservation.start_date <= end_date,
+        or_(
+            JobReservation.end_date >= start_date,
+            JobReservation.end_date == None  # TBD reservations
+        )
+    ).order_by(JobReservation.start_date).all()
+
+    # Get assignment counts
+    reservation_data = []
+    for res in reservations:
+        assigned_count = db.query(JobReservationUnit).filter_by(
+            reservation_id=res.id
+        ).count()
+
+        # Check for calibration conflicts
+        conflicts = check_calibration_conflicts(db, res.id)
+
+        reservation_data.append({
+            "reservation": res,
+            "assigned_count": assigned_count,
+            "has_conflicts": len(conflicts) > 0,
+            "conflict_count": len(conflicts)
+        })
+
+    return templates.TemplateResponse(
+        "partials/fleet_calendar/reservations_list.html",
+        {
+            "request": request,
+            "reservations": reservation_data,
+            "year": year,
+            "device_type": device_type
+        }
+    )
+
+
+@router.get("/api/fleet-calendar/available-units", response_class=HTMLResponse)
+async def get_available_units_partial(
+    request: Request,
+    start_date: str,
+    end_date: str,
+    device_type: str = "seismograph",
+    reservation_id: Optional[str] = None,
+    db: Session = Depends(get_db)
+):
+    """Get available units as HTMX partial for the assignment modal."""
+    try:
+        start = date.fromisoformat(start_date)
+        end = date.fromisoformat(end_date)
+    except ValueError:
+        raise HTTPException(status_code=400, detail="Invalid date format")
+
+    available = get_available_units_for_period(
+        db, start, end, device_type, reservation_id
+    )
+
+    return templates.TemplateResponse(
+        "partials/fleet_calendar/available_units.html",
+        {
+            "request": request,
+            "units": available,
+            "start_date": start_date,
+            "end_date": end_date,
+            "device_type": device_type,
+            "reservation_id": reservation_id
+        }
+    )
+
+
+@router.get("/api/fleet-calendar/month/{year}/{month}", response_class=HTMLResponse)
+async def get_month_partial(
+    request: Request,
+    year: int,
+    month: int,
+    device_type: str = "seismograph",
+    db: Session = Depends(get_db)
+):
+    """Get a single month calendar as HTMX partial."""
+    calendar_data = get_calendar_year_data(db, year, device_type)
+    month_data = calendar_data["months"].get(month)
+
+    if not month_data:
+        raise HTTPException(status_code=404, detail="Invalid month")
+
+    return templates.TemplateResponse(
+        "partials/fleet_calendar/month_grid.html",
+        {
+            "request": request,
+            "year": year,
+            "month": month,
+            "month_data": month_data,
+            "device_type": device_type,
+            "today": date.today().isoformat()
+        }
+    )

backend/routers/roster_edit.py

@@ -1,7 +1,7 @@
 from fastapi import APIRouter, Depends, HTTPException, Form, UploadFile, File, Request, Query
 from fastapi.exceptions import RequestValidationError
 from sqlalchemy.orm import Session
-from datetime import datetime, date
+from datetime import datetime, date, timedelta
 import csv
 import io
 import logging
@@ -185,8 +185,13 @@ async def add_roster_unit(
         except ValueError:
             raise HTTPException(status_code=400, detail="Invalid last_calibrated date format. Use YYYY-MM-DD")
 
+    # Auto-calculate next_calibration_due (1 year from last_calibrated)
+    # This is calculated internally but not shown to user (they just see last_calibrated)
     next_cal_date = None
-    if next_calibration_due:
+    if last_cal_date:
+        next_cal_date = last_cal_date + timedelta(days=365)
+    elif next_calibration_due:
+        # Fallback: allow explicit setting if no last_calibrated
         try:
             next_cal_date = datetime.strptime(next_calibration_due, "%Y-%m-%d").date()
         except ValueError:
@@ -517,8 +522,13 @@ async def edit_roster_unit(
         except ValueError:
             raise HTTPException(status_code=400, detail="Invalid last_calibrated date format. Use YYYY-MM-DD")
 
+    # Auto-calculate next_calibration_due (1 year from last_calibrated)
+    # This is calculated internally but not shown to user (they just see last_calibrated)
     next_cal_date = None
-    if next_calibration_due:
+    if last_cal_date:
+        next_cal_date = last_cal_date + timedelta(days=365)
+    elif next_calibration_due:
+        # Fallback: allow explicit setting if no last_calibrated
         try:
             next_cal_date = datetime.strptime(next_calibration_due, "%Y-%m-%d").date()
         except ValueError:
@@ -995,8 +1005,13 @@ async def import_csv(
 
                 # Seismograph-specific fields
                 if row.get('last_calibrated'):
-                    existing_unit.last_calibrated = _parse_date(row.get('last_calibrated'))
-                if row.get('next_calibration_due'):
+                    last_cal = _parse_date(row.get('last_calibrated'))
+                    existing_unit.last_calibrated = last_cal
+                    # Auto-calculate next_calibration_due (1 year from last_calibrated)
+                    if last_cal:
+                                        existing_unit.next_calibration_due = last_cal + timedelta(days=365)
+                elif row.get('next_calibration_due'):
+                    # Only use explicit next_calibration_due if no last_calibrated
                     existing_unit.next_calibration_due = _parse_date(row.get('next_calibration_due'))
                 if row.get('deployed_with_modem_id'):
                     existing_unit.deployed_with_modem_id = _get_csv_value(row, 'deployed_with_modem_id')
@@ -1046,9 +1061,13 @@ async def import_csv(
                     address=_get_csv_value(row, 'address'),
                     coordinates=_get_csv_value(row, 'coordinates'),
                     last_updated=datetime.utcnow(),
-                    # Seismograph fields
+                    # Seismograph fields - auto-calc next_calibration_due from last_calibrated
                     last_calibrated=_parse_date(row.get('last_calibrated', '')),
-                    next_calibration_due=_parse_date(row.get('next_calibration_due', '')),
+                    next_calibration_due=(
+                        _parse_date(row.get('last_calibrated', '')) + timedelta(days=365)
+                        if _parse_date(row.get('last_calibrated', ''))
+                        else _parse_date(row.get('next_calibration_due', ''))
+                    ),
                     deployed_with_modem_id=_get_csv_value(row, 'deployed_with_modem_id'),
                     # Modem fields
                     ip_address=_get_csv_value(row, 'ip_address'),

backend/services/fleet_calendar_service.py

@@ -0,0 +1,668 @@
+"""
+Fleet Calendar Service
+
+Business logic for:
+- Calculating unit availability on any given date
+- Calibration status tracking (valid, expiring soon, expired)
+- Job reservation management
+- Conflict detection (calibration expires mid-job)
+"""
+
+from datetime import date, datetime, timedelta
+from typing import Dict, List, Optional, Tuple
+from sqlalchemy.orm import Session
+from sqlalchemy import and_, or_
+
+from backend.models import (
+    RosterUnit, JobReservation, JobReservationUnit,
+    UserPreferences, Project
+)
+
+
+def get_calibration_status(
+    unit: RosterUnit,
+    check_date: date,
+    warning_days: int = 30
+) -> str:
+    """
+    Determine calibration status for a unit on a specific date.
+
+    Returns:
+        "valid" - Calibration is good on this date
+        "expiring_soon" - Within warning_days of expiry
+        "expired" - Calibration has expired
+        "needs_calibration" - No calibration date set
+    """
+    if not unit.last_calibrated:
+        return "needs_calibration"
+
+    # Calculate expiry date (1 year from last calibration)
+    expiry_date = unit.last_calibrated + timedelta(days=365)
+
+    if check_date >= expiry_date:
+        return "expired"
+    elif check_date >= expiry_date - timedelta(days=warning_days):
+        return "expiring_soon"
+    else:
+        return "valid"
+
+
+def get_unit_reservations_on_date(
+    db: Session,
+    unit_id: str,
+    check_date: date
+) -> List[JobReservation]:
+    """Get all reservations that include this unit on the given date."""
+
+    # Get reservation IDs that have this unit assigned
+    assigned_reservation_ids = db.query(JobReservationUnit.reservation_id).filter(
+        JobReservationUnit.unit_id == unit_id
+    ).subquery()
+
+    # Get reservations that:
+    # 1. Have this unit assigned AND date is within range
+    reservations = db.query(JobReservation).filter(
+        JobReservation.id.in_(assigned_reservation_ids),
+        JobReservation.start_date <= check_date,
+        JobReservation.end_date >= check_date
+    ).all()
+
+    return reservations
+
+
+def is_unit_available_on_date(
+    db: Session,
+    unit: RosterUnit,
+    check_date: date,
+    warning_days: int = 30
+) -> Tuple[bool, str, Optional[str]]:
+    """
+    Check if a unit is available on a specific date.
+
+    Returns:
+        (is_available, status, reservation_name)
+        - is_available: True if unit can be assigned to new work
+        - status: "available", "reserved", "expired", "retired", "needs_calibration"
+        - reservation_name: Name of blocking reservation (if any)
+    """
+    # Check if retired
+    if unit.retired:
+        return False, "retired", None
+
+    # Check calibration status
+    cal_status = get_calibration_status(unit, check_date, warning_days)
+    if cal_status == "expired":
+        return False, "expired", None
+    if cal_status == "needs_calibration":
+        return False, "needs_calibration", None
+
+    # Check if already reserved
+    reservations = get_unit_reservations_on_date(db, unit.id, check_date)
+    if reservations:
+        return False, "reserved", reservations[0].name
+
+    # Unit is available (even if expiring soon - that's just a warning)
+    return True, "available", None
+
+
+def get_day_summary(
+    db: Session,
+    check_date: date,
+    device_type: str = "seismograph"
+) -> Dict:
+    """
+    Get a complete summary of fleet status for a specific day.
+
+    Returns dict with:
+        - available_units: List of available unit IDs with calibration info
+        - reserved_units: List of reserved unit IDs with reservation info
+        - expired_units: List of units with expired calibration
+        - expiring_soon_units: List of units expiring within warning period
+        - reservations: List of active reservations on this date
+        - counts: Summary counts
+    """
+    # Get user preferences for warning days
+    prefs = db.query(UserPreferences).filter_by(id=1).first()
+    warning_days = prefs.calibration_warning_days if prefs else 30
+
+    # Get all non-retired units of the specified device type
+    units = db.query(RosterUnit).filter(
+        RosterUnit.device_type == device_type,
+        RosterUnit.retired == False
+    ).all()
+
+    available_units = []
+    reserved_units = []
+    expired_units = []
+    expiring_soon_units = []
+    needs_calibration_units = []
+    cal_expiring_today = []  # Units whose calibration expires ON this day
+
+    for unit in units:
+        is_avail, status, reservation_name = is_unit_available_on_date(
+            db, unit, check_date, warning_days
+        )
+
+        cal_status = get_calibration_status(unit, check_date, warning_days)
+        expiry_date = None
+        if unit.last_calibrated:
+            expiry_date = (unit.last_calibrated + timedelta(days=365)).isoformat()
+
+        unit_info = {
+            "id": unit.id,
+            "last_calibrated": unit.last_calibrated.isoformat() if unit.last_calibrated else None,
+            "expiry_date": expiry_date,
+            "calibration_status": cal_status,
+            "deployed": unit.deployed,
+            "note": unit.note or ""
+        }
+
+        # Check if calibration expires ON this specific day
+        if unit.last_calibrated:
+            unit_expiry_date = unit.last_calibrated + timedelta(days=365)
+            if unit_expiry_date == check_date:
+                cal_expiring_today.append(unit_info)
+
+        if status == "available":
+            available_units.append(unit_info)
+            if cal_status == "expiring_soon":
+                expiring_soon_units.append(unit_info)
+        elif status == "reserved":
+            unit_info["reservation_name"] = reservation_name
+            reserved_units.append(unit_info)
+            if cal_status == "expiring_soon":
+                expiring_soon_units.append(unit_info)
+        elif status == "expired":
+            expired_units.append(unit_info)
+        elif status == "needs_calibration":
+            needs_calibration_units.append(unit_info)
+
+    # Get active reservations on this date
+    reservations = db.query(JobReservation).filter(
+        JobReservation.device_type == device_type,
+        JobReservation.start_date <= check_date,
+        JobReservation.end_date >= check_date
+    ).all()
+
+    reservation_list = []
+    for res in reservations:
+        # Count assigned units for this reservation
+        assigned_count = db.query(JobReservationUnit).filter(
+            JobReservationUnit.reservation_id == res.id
+        ).count()
+
+        reservation_list.append({
+            "id": res.id,
+            "name": res.name,
+            "start_date": res.start_date.isoformat(),
+            "end_date": res.end_date.isoformat(),
+            "assignment_type": res.assignment_type,
+            "quantity_needed": res.quantity_needed,
+            "assigned_count": assigned_count,
+            "color": res.color,
+            "project_id": res.project_id
+        })
+
+    return {
+        "date": check_date.isoformat(),
+        "device_type": device_type,
+        "available_units": available_units,
+        "reserved_units": reserved_units,
+        "expired_units": expired_units,
+        "expiring_soon_units": expiring_soon_units,
+        "needs_calibration_units": needs_calibration_units,
+        "cal_expiring_today": cal_expiring_today,
+        "reservations": reservation_list,
+        "counts": {
+            "available": len(available_units),
+            "reserved": len(reserved_units),
+            "expired": len(expired_units),
+            "expiring_soon": len(expiring_soon_units),
+            "needs_calibration": len(needs_calibration_units),
+            "cal_expiring_today": len(cal_expiring_today),
+            "total": len(units)
+        }
+    }
+
+
+def get_calendar_year_data(
+    db: Session,
+    year: int,
+    device_type: str = "seismograph"
+) -> Dict:
+    """
+    Get calendar data for an entire year.
+
+    For performance, this returns summary counts per day rather than
+    full unit lists. Use get_day_summary() for detailed day data.
+    """
+    # Get user preferences
+    prefs = db.query(UserPreferences).filter_by(id=1).first()
+    warning_days = prefs.calibration_warning_days if prefs else 30
+
+    # Get all units
+    units = db.query(RosterUnit).filter(
+        RosterUnit.device_type == device_type,
+        RosterUnit.retired == False
+    ).all()
+
+    # Get all reservations that overlap with this year
+    # Include TBD reservations (end_date is null) that started before year end
+    year_start = date(year, 1, 1)
+    year_end = date(year, 12, 31)
+
+    reservations = db.query(JobReservation).filter(
+        JobReservation.device_type == device_type,
+        JobReservation.start_date <= year_end,
+        or_(
+            JobReservation.end_date >= year_start,
+            JobReservation.end_date == None  # TBD reservations
+        )
+    ).all()
+
+    # Get all unit assignments for these reservations
+    reservation_ids = [r.id for r in reservations]
+    assignments = db.query(JobReservationUnit).filter(
+        JobReservationUnit.reservation_id.in_(reservation_ids)
+    ).all() if reservation_ids else []
+
+    # Build a lookup: unit_id -> list of (start_date, end_date, reservation_name)
+    # For TBD reservations, use estimated_end_date if available, or a far future date
+    unit_reservations = {}
+    for res in reservations:
+        res_assignments = [a for a in assignments if a.reservation_id == res.id]
+        for assignment in res_assignments:
+            unit_id = assignment.unit_id
+            # Use unit-specific dates if set, otherwise use reservation dates
+            start_d = assignment.unit_start_date or res.start_date
+            if assignment.unit_end_tbd or (assignment.unit_end_date is None and res.end_date_tbd):
+                # TBD: use estimated date or far future for availability calculation
+                end_d = res.estimated_end_date or date(year + 5, 12, 31)
+            else:
+                end_d = assignment.unit_end_date or res.end_date or date(year + 5, 12, 31)
+
+            if unit_id not in unit_reservations:
+                unit_reservations[unit_id] = []
+            unit_reservations[unit_id].append((start_d, end_d, res.name))
+
+    # Generate data for each month
+    months_data = {}
+
+    for month in range(1, 13):
+        # Get first and last day of month
+        first_day = date(year, month, 1)
+        if month == 12:
+            last_day = date(year, 12, 31)
+        else:
+            last_day = date(year, month + 1, 1) - timedelta(days=1)
+
+        days_data = {}
+        current_day = first_day
+
+        while current_day <= last_day:
+            available = 0
+            reserved = 0
+            expired = 0
+            expiring_soon = 0
+            needs_cal = 0
+            cal_expiring_on_day = 0  # Units whose calibration expires ON this day
+            cal_expired_on_day = 0   # Units whose calibration expired ON this day
+
+            for unit in units:
+                # Check calibration
+                cal_status = get_calibration_status(unit, current_day, warning_days)
+
+                # Check if calibration expires/expired ON this specific day
+                if unit.last_calibrated:
+                    unit_expiry = unit.last_calibrated + timedelta(days=365)
+                    if unit_expiry == current_day:
+                        cal_expiring_on_day += 1
+                    # Check if expired yesterday (first day of being expired)
+                    elif unit_expiry == current_day - timedelta(days=1):
+                        cal_expired_on_day += 1
+
+                if cal_status == "expired":
+                    expired += 1
+                    continue
+                if cal_status == "needs_calibration":
+                    needs_cal += 1
+                    continue
+
+                # Check if reserved
+                is_reserved = False
+                if unit.id in unit_reservations:
+                    for start_d, end_d, _ in unit_reservations[unit.id]:
+                        if start_d <= current_day <= end_d:
+                            is_reserved = True
+                            break
+
+                if is_reserved:
+                    reserved += 1
+                else:
+                    available += 1
+
+                if cal_status == "expiring_soon":
+                    expiring_soon += 1
+
+            days_data[current_day.day] = {
+                "available": available,
+                "reserved": reserved,
+                "expired": expired,
+                "expiring_soon": expiring_soon,
+                "needs_calibration": needs_cal,
+                "cal_expiring_on_day": cal_expiring_on_day,
+                "cal_expired_on_day": cal_expired_on_day
+            }
+
+            current_day += timedelta(days=1)
+
+        months_data[month] = {
+            "name": first_day.strftime("%B"),
+            "short_name": first_day.strftime("%b"),
+            "days": days_data,
+            "first_weekday": first_day.weekday(),  # 0=Monday, 6=Sunday
+            "num_days": last_day.day
+        }
+
+    # Also include reservation summary for the year
+    reservation_list = []
+    for res in reservations:
+        assigned_count = len([a for a in assignments if a.reservation_id == res.id])
+        reservation_list.append({
+            "id": res.id,
+            "name": res.name,
+            "start_date": res.start_date.isoformat(),
+            "end_date": res.end_date.isoformat(),
+            "quantity_needed": res.quantity_needed,
+            "assigned_count": assigned_count,
+            "color": res.color
+        })
+
+    return {
+        "year": year,
+        "device_type": device_type,
+        "months": months_data,
+        "reservations": reservation_list,
+        "total_units": len(units)
+    }
+
+
+def get_rolling_calendar_data(
+    db: Session,
+    start_year: int,
+    start_month: int,
+    device_type: str = "seismograph"
+) -> Dict:
+    """
+    Get calendar data for 12 months starting from a specific month/year.
+
+    This supports the rolling calendar view where users can scroll through
+    months one at a time, viewing any 12-month window.
+    """
+    # Get user preferences
+    prefs = db.query(UserPreferences).filter_by(id=1).first()
+    warning_days = prefs.calibration_warning_days if prefs else 30
+
+    # Get all units
+    units = db.query(RosterUnit).filter(
+        RosterUnit.device_type == device_type,
+        RosterUnit.retired == False
+    ).all()
+
+    # Calculate the date range for 12 months
+    first_date = date(start_year, start_month, 1)
+    # Calculate end date (12 months later)
+    end_year = start_year + 1 if start_month == 1 else start_year
+    end_month = 12 if start_month == 1 else start_month - 1
+    if start_month == 1:
+        end_year = start_year
+        end_month = 12
+    else:
+        # 12 months from start_month means we end at start_month - 1 next year
+        end_year = start_year + 1
+        end_month = start_month - 1
+
+    # Actually, simpler: go 11 months forward from start
+    end_year = start_year + ((start_month + 10) // 12)
+    end_month = ((start_month + 10) % 12) + 1
+    if end_month == 12:
+        last_date = date(end_year, 12, 31)
+    else:
+        last_date = date(end_year, end_month + 1, 1) - timedelta(days=1)
+
+    # Get all reservations that overlap with this 12-month range
+    reservations = db.query(JobReservation).filter(
+        JobReservation.device_type == device_type,
+        JobReservation.start_date <= last_date,
+        or_(
+            JobReservation.end_date >= first_date,
+            JobReservation.end_date == None  # TBD reservations
+        )
+    ).all()
+
+    # Get all unit assignments for these reservations
+    reservation_ids = [r.id for r in reservations]
+    assignments = db.query(JobReservationUnit).filter(
+        JobReservationUnit.reservation_id.in_(reservation_ids)
+    ).all() if reservation_ids else []
+
+    # Build a lookup: unit_id -> list of (start_date, end_date, reservation_name)
+    unit_reservations = {}
+    for res in reservations:
+        res_assignments = [a for a in assignments if a.reservation_id == res.id]
+        for assignment in res_assignments:
+            unit_id = assignment.unit_id
+            start_d = assignment.unit_start_date or res.start_date
+            if assignment.unit_end_tbd or (assignment.unit_end_date is None and res.end_date_tbd):
+                end_d = res.estimated_end_date or date(start_year + 5, 12, 31)
+            else:
+                end_d = assignment.unit_end_date or res.end_date or date(start_year + 5, 12, 31)
+
+            if unit_id not in unit_reservations:
+                unit_reservations[unit_id] = []
+            unit_reservations[unit_id].append((start_d, end_d, res.name))
+
+    # Generate data for each of the 12 months
+    months_data = []
+    current_year = start_year
+    current_month = start_month
+
+    for i in range(12):
+        # Calculate this month's year and month
+        m_year = start_year + ((start_month - 1 + i) // 12)
+        m_month = ((start_month - 1 + i) % 12) + 1
+
+        first_day = date(m_year, m_month, 1)
+        if m_month == 12:
+            last_day = date(m_year, 12, 31)
+        else:
+            last_day = date(m_year, m_month + 1, 1) - timedelta(days=1)
+
+        days_data = {}
+        current_day = first_day
+
+        while current_day <= last_day:
+            available = 0
+            reserved = 0
+            expired = 0
+            expiring_soon = 0
+            needs_cal = 0
+            cal_expiring_on_day = 0
+            cal_expired_on_day = 0
+
+            for unit in units:
+                cal_status = get_calibration_status(unit, current_day, warning_days)
+
+                if unit.last_calibrated:
+                    unit_expiry = unit.last_calibrated + timedelta(days=365)
+                    if unit_expiry == current_day:
+                        cal_expiring_on_day += 1
+                    elif unit_expiry == current_day - timedelta(days=1):
+                        cal_expired_on_day += 1
+
+                if cal_status == "expired":
+                    expired += 1
+                    continue
+                if cal_status == "needs_calibration":
+                    needs_cal += 1
+                    continue
+
+                is_reserved = False
+                if unit.id in unit_reservations:
+                    for start_d, end_d, _ in unit_reservations[unit.id]:
+                        if start_d <= current_day <= end_d:
+                            is_reserved = True
+                            break
+
+                if is_reserved:
+                    reserved += 1
+                else:
+                    available += 1
+
+                if cal_status == "expiring_soon":
+                    expiring_soon += 1
+
+            days_data[current_day.day] = {
+                "available": available,
+                "reserved": reserved,
+                "expired": expired,
+                "expiring_soon": expiring_soon,
+                "needs_calibration": needs_cal,
+                "cal_expiring_on_day": cal_expiring_on_day,
+                "cal_expired_on_day": cal_expired_on_day
+            }
+
+            current_day += timedelta(days=1)
+
+        months_data.append({
+            "year": m_year,
+            "month": m_month,
+            "name": first_day.strftime("%B"),
+            "short_name": first_day.strftime("%b"),
+            "year_short": first_day.strftime("%y"),
+            "days": days_data,
+            "first_weekday": first_day.weekday(),
+            "num_days": last_day.day
+        })
+
+    return {
+        "start_year": start_year,
+        "start_month": start_month,
+        "device_type": device_type,
+        "months": months_data,
+        "total_units": len(units)
+    }
+
+
+def check_calibration_conflicts(
+    db: Session,
+    reservation_id: str
+) -> List[Dict]:
+    """
+    Check if any units assigned to a reservation will have their
+    calibration expire during the reservation period.
+
+    Returns list of conflicts with unit info and expiry date.
+    """
+    reservation = db.query(JobReservation).filter_by(id=reservation_id).first()
+    if not reservation:
+        return []
+
+    # Get assigned units
+    assigned = db.query(JobReservationUnit).filter_by(
+        reservation_id=reservation_id
+    ).all()
+
+    conflicts = []
+    for assignment in assigned:
+        unit = db.query(RosterUnit).filter_by(id=assignment.unit_id).first()
+        if not unit or not unit.last_calibrated:
+            continue
+
+        expiry_date = unit.last_calibrated + timedelta(days=365)
+
+        # Check if expiry falls within reservation period
+        if reservation.start_date < expiry_date <= reservation.end_date:
+            conflicts.append({
+                "unit_id": unit.id,
+                "last_calibrated": unit.last_calibrated.isoformat(),
+                "expiry_date": expiry_date.isoformat(),
+                "reservation_name": reservation.name,
+                "days_into_job": (expiry_date - reservation.start_date).days
+            })
+
+    return conflicts
+
+
+def get_available_units_for_period(
+    db: Session,
+    start_date: date,
+    end_date: date,
+    device_type: str = "seismograph",
+    exclude_reservation_id: Optional[str] = None
+) -> List[Dict]:
+    """
+    Get units that are available for the entire specified period.
+
+    A unit is available if:
+    - Not retired
+    - Calibration is valid through the end date
+    - Not assigned to any other reservation that overlaps the period
+    """
+    prefs = db.query(UserPreferences).filter_by(id=1).first()
+    warning_days = prefs.calibration_warning_days if prefs else 30
+
+    units = db.query(RosterUnit).filter(
+        RosterUnit.device_type == device_type,
+        RosterUnit.retired == False
+    ).all()
+
+    # Get reservations that overlap with this period
+    overlapping_reservations = db.query(JobReservation).filter(
+        JobReservation.device_type == device_type,
+        JobReservation.start_date <= end_date,
+        JobReservation.end_date >= start_date
+    )
+
+    if exclude_reservation_id:
+        overlapping_reservations = overlapping_reservations.filter(
+            JobReservation.id != exclude_reservation_id
+        )
+
+    overlapping_reservations = overlapping_reservations.all()
+
+    # Get all units assigned to overlapping reservations
+    reserved_unit_ids = set()
+    for res in overlapping_reservations:
+        assigned = db.query(JobReservationUnit).filter_by(
+            reservation_id=res.id
+        ).all()
+        for a in assigned:
+            reserved_unit_ids.add(a.unit_id)
+
+    available_units = []
+    for unit in units:
+        # Check if already reserved
+        if unit.id in reserved_unit_ids:
+            continue
+
+        # Check calibration through end of period
+        if not unit.last_calibrated:
+            continue  # Needs calibration
+
+        expiry_date = unit.last_calibrated + timedelta(days=365)
+        if expiry_date <= end_date:
+            continue  # Calibration expires during period
+
+        cal_status = get_calibration_status(unit, end_date, warning_days)
+
+        available_units.append({
+            "id": unit.id,
+            "last_calibrated": unit.last_calibrated.isoformat(),
+            "expiry_date": expiry_date.isoformat(),
+            "calibration_status": cal_status,
+            "deployed": unit.deployed,
+            "note": unit.note or ""
+        })
+
+    return available_units

backend/services/slm_status_sync.py

@@ -70,6 +70,10 @@ async def sync_slm_status_to_emitters() -> Dict[str, Any]:
                         # Convert to naive UTC for consistency with existing code
                         if last_seen.tzinfo:
                             last_seen = last_seen.astimezone(timezone.utc).replace(tzinfo=None)
+                    elif is_reachable:
+                        # Device is reachable but no last_success yet (first poll or just started)
+                        # Use current time so it shows as OK, not Missing
+                        last_seen = datetime.utcnow()
                     else:
                         last_seen = None