Changes Made

1. config/schema.sql — Added timezone_name VARCHAR(100) to user_preferences table + an ALTER TABLE migration at the bottom for existing DBs.
  2. core/tz.py — Rewrote with dual-path timezone support:
  - Request context: _get_request_tz() now checks X-Timezone-Name header (IANA) first, falls back to X-Timezone-Offset
  - Background jobs: New tz_for_user(user_uuid) and user_now_for(user_uuid) read stored timezone_name from prefs, fall back to numeric offset, then UTC
  - All existing function signatures (user_now(), user_today()) preserved for backward compat

  3. scheduler/daemon.py — Fixed 3 bugs:
  - _user_now_for() now delegates to tz.user_now_for() which uses IANA timezone names (DST-safe)
  - check_nagging() — replaced datetime.utcnow() with _user_now_for(user_uuid) so nags evaluate in user's timezone
  - poll_callback() — replaced single UTC midnight check with _check_per_user_midnight_schedules() that iterates users and creates daily schedules at their local midnight

  4. api/routes/preferences.py — Added "timezone_name" to allowed PUT fields.

  5. synculous-client/src/lib/api.ts — Added X-Timezone-Name header to every request + added timezone_name to preferences update type.

  6. synculous-client/src/app/dashboard/layout.tsx — Now syncs both timezone_offset and timezone_name (via Intl.DateTimeFormat().resolvedOptions().timeZone) on session start.

scheduler/daemon.py

@@ -13,6 +13,7 @@ import core.postgres as postgres
 import core.notifications as notifications
 import core.adaptive_meds as adaptive_meds
 import core.snitch as snitch
+import core.tz as tz
 
 logging.basicConfig(level=logging.INFO)
 logger = logging.getLogger(__name__)
@@ -21,14 +22,8 @@ POLL_INTERVAL = int(os.environ.get("POLL_INTERVAL", 60))
 
 
 def _user_now_for(user_uuid):
-    """Get current datetime in a user's timezone using their stored offset."""
-    prefs = postgres.select_one("user_preferences", {"user_uuid": user_uuid})
-    offset_minutes = 0
-    if prefs and prefs.get("timezone_offset") is not None:
-        offset_minutes = prefs["timezone_offset"]
-    # JS getTimezoneOffset: positive = behind UTC, so negate
-    tz_obj = timezone(timedelta(minutes=-offset_minutes))
-    return datetime.now(tz_obj)
+    """Get current datetime in a user's timezone using their stored preferences."""
+    return tz.user_now_for(user_uuid)
 
 
 def check_medication_reminders():
@@ -158,7 +153,8 @@ def check_refills():
 
 
 def create_daily_adaptive_schedules():
-    """Create today's medication schedules with adaptive timing."""
+    """Create today's medication schedules with adaptive timing.
+    Called per-user when it's midnight in their timezone."""
     try:
         from datetime import date as date_type
 
@@ -312,7 +308,7 @@ def check_nagging():
                 logger.debug(f"Nagging disabled for user {user_uuid}")
                 continue
 
-            now = datetime.utcnow()
+            now = _user_now_for(user_uuid)
             today = now.date()
 
             # Get today's schedules
@@ -428,18 +424,55 @@ def check_nagging():
         logger.error(f"Error checking nags: {e}")
 
 
-def poll_callback():
-    """Called every POLL_INTERVAL seconds."""
-    # Create daily schedules at midnight
-    now = datetime.utcnow()
-    if now.hour == 0 and now.minute < POLL_INTERVAL / 60:
+def _get_distinct_user_uuids():
+    """Return a set of user UUIDs that have active medications or routines."""
+    uuids = set()
+    try:
+        meds = postgres.select("medications", where={"active": True})
+        for m in meds:
+            uid = m.get("user_uuid")
+            if uid:
+                uuids.add(uid)
+    except Exception:
+        pass
+    try:
+        routines = postgres.select("routines")
+        for r in routines:
+            uid = r.get("user_uuid")
+            if uid:
+                uuids.add(uid)
+    except Exception:
+        pass
+    return uuids
+
+
+def _check_per_user_midnight_schedules():
+    """Create daily adaptive schedules for each user when it's midnight in
+    their timezone (within the poll window)."""
+    for user_uuid in _get_distinct_user_uuids():
         try:
-            create_daily_adaptive_schedules()
+            now = _user_now_for(user_uuid)
+            if now.hour == 0 and now.minute < POLL_INTERVAL / 60:
+                user_meds = postgres.select(
+                    "medications", where={"user_uuid": user_uuid, "active": True}
+                )
+                for med in user_meds:
+                    times = med.get("times", [])
+                    if times:
+                        adaptive_meds.create_daily_schedule(
+                            user_uuid, med["id"], times
+                        )
         except Exception as e:
             logger.warning(
-                f"Could not create adaptive schedules (tables may not exist): {e}"
+                f"Could not create adaptive schedules for user {user_uuid}: {e}"
             )
 
+
+def poll_callback():
+    """Called every POLL_INTERVAL seconds."""
+    # Create daily schedules per-user at their local midnight
+    _check_per_user_midnight_schedules()
+
     # Check reminders - use both original and adaptive checks
     logger.info("Checking medication reminders")
     check_medication_reminders()