# Plan: Fix Timezone Handling in Wakeup Times Module

## Problem Description
The "Wakeup Times" chart (in `frontend/src/components/stats/WakeupPlot.tsx`) displays wakeup times incorrectly due to a timezone mismatch. 
- **Observation**: If a baby wakes up at `05:55` local time (e.g., in UTC+2), the chart shows `03:55`.
- **Cause**: The backend stores times in UTC. The frontend currently receives minutes relative to UTC midnight and renders them directly using `formatMinutesAfter` without applying the client's local timezone offset.

## Investigation Steps
1. **Backend Verification**: 
   - Examine `backend/app/routers/stats.py` (or equivalent) and the CRUD logic to confirm that `wakeup_minutes` is calculated based on UTC midnight.
   - Verify how the backend handles the `wakeup_ref` and `bedtime_ref` parameters.
2. **Frontend Logic Audit**: 
   - Trace the data flow from `fetchWakeSleepTimes` -> `useStats` -> `WakeupPlot.tsx`.
   - Confirm that `wakeup_minutes` is indeed a raw offset from UTC midnight.

## Implementation Plan
1. **Calculate Local Offset**: Use `new Date().getTimezoneOffset()` in the frontend to determine the difference between UTC and local time.
2. **Adjust Minutes**: 
   - In `WakeupPlot.tsx`, modify the mapping logic to adjust `day.wakeup_minutes` by the local timezone offset before it is passed to `formatMinutesAfter`.
   - Formula: `local_minutes = utc_minutes - (timezone_offset_in_minutes)`. 
     *(Note: `getTimezoneOffset()` returns minutes positive for west of UTC, negative for east, so subtraction is correct to add offset to UTC).*
3. **Refactor Utilities (if needed)**: If the logic is used elsewhere, consider moving timezone-aware formatting to `frontend/src/utils/time.ts`.

## Verification Plan
1. **Manual Verification**: 
   - Mock a response from the backend with a known UTC time.
   - Check if the rendered string matches the expected local time.
2. **Automated Testing**: 
   - Add/update a test case in `frontend/tests/e2e/stats.spec.ts` (or a unit test in `frontend/tests/`) that simulates different timezone offsets to ensure the display is correct.
3. **Regression Check**: 
   - Ensure `BedtimePlot.tsx` and other time-related components are not negatively impacted by changes to shared utilities.