Fix snooze/due using container UTC instead of client local time

Docker container datetime.now() returns UTC, but all stored datetimes
are naive local time from the browser. Both /due and /snooze now
accept client_now from the frontend, ensuring snooze computes from
the user's actual current time, not the container's clock.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/routers/reminders.py

@@ -40,11 +40,12 @@ async def get_reminders(
 
 @router.get("/due", response_model=List[ReminderResponse])
 async def get_due_reminders(
+    client_now: Optional[datetime] = Query(None),
     db: AsyncSession = Depends(get_db),
     current_user: Settings = Depends(get_current_session)
 ):
     """Get reminders that are currently due for alerting."""
-    now = datetime.now()
+    now = client_now or datetime.now()
     query = select(Reminder).where(
         and_(
             Reminder.remind_at <= now,
@@ -82,7 +83,8 @@ async def snooze_reminder(
     if reminder.is_dismissed or not reminder.is_active:
         raise HTTPException(status_code=409, detail="Cannot snooze a dismissed or inactive reminder")
 
-    reminder.snoozed_until = datetime.now() + timedelta(minutes=body.minutes)
+    base_time = body.client_now or datetime.now()
+    reminder.snoozed_until = base_time + timedelta(minutes=body.minutes)
 
     await db.commit()
     await db.refresh(reminder)

backend/app/schemas/reminder.py

@@ -22,6 +22,7 @@ class ReminderUpdate(BaseModel):
 
 class ReminderSnooze(BaseModel):
     minutes: Literal[5, 10, 15]
+    client_now: Optional[datetime] = None
 
     @field_validator('minutes', mode='before')
     @classmethod

frontend/src/hooks/useAlerts.tsx

@@ -4,7 +4,7 @@ import { useLocation } from 'react-router-dom';
 import { toast } from 'sonner';
 import { Bell } from 'lucide-react';
 import api from '@/lib/api';
-import { getRelativeTime } from '@/lib/date-utils';
+import { getRelativeTime, toLocalDatetime } from '@/lib/date-utils';
 import SnoozeDropdown from '@/components/reminders/SnoozeDropdown';
 import type { Reminder } from '@/types';
 
@@ -36,7 +36,9 @@ export function AlertsProvider({ children }: { children: ReactNode }) {
   const { data: alerts = [] } = useQuery<Reminder[]>({
     queryKey: ['reminders', 'due'],
     queryFn: async () => {
-      const { data } = await api.get<Reminder[]>('/reminders/due');
+      const { data } = await api.get<Reminder[]>('/reminders/due', {
+        params: { client_now: toLocalDatetime() },
+      });
       return data;
     },
     refetchInterval: 30_000,
@@ -66,7 +68,7 @@ export function AlertsProvider({ children }: { children: ReactNode }) {
 
   const snoozeMutation = useMutation({
     mutationFn: ({ id, minutes }: { id: number; minutes: 5 | 10 | 15 }) =>
-      api.patch(`/reminders/${id}/snooze`, { minutes }),
+      api.patch(`/reminders/${id}/snooze`, { minutes, client_now: toLocalDatetime() }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['reminders'] });
       queryClient.invalidateQueries({ queryKey: ['dashboard'] });

frontend/src/lib/date-utils.ts

@@ -1,3 +1,9 @@
+/** Format a Date as a naive local datetime string (no Z suffix). */
+export function toLocalDatetime(d: Date = new Date()): string {
+  const pad = (n: number) => n.toString().padStart(2, '0');
+  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T${pad(d.getHours())}:${pad(d.getMinutes())}:${pad(d.getSeconds())}`;
+}
+
 export function getRelativeTime(dateStr: string): string {
   const date = new Date(dateStr);
   const now = new Date();