Time bugs: zones and daylight saving

You never edit code first. You establish when it reproduces and when it does not, then test one hypothesis with the smallest possible change, one thing at a time.

Task: A scheduled job runs at the wrong time, or timestamps are off by eight hours.

[Before you start, do three things]
1. Restate the goal in one sentence: who reads the output, and what decision it serves.
2. If I have not given you the following, ask me. Do not assume:
   - stored type and zone
   - display zone
   - regions with daylight saving
3. Say how you plan to do it (at most 5 steps) and wait for my go-ahead.

[Go through each of these]
- decide UTC or local for storage and say why
- list every conversion point in the code
- check scheduler zone versus execution zone
- state how duplicated or missing hours are handled

[Process]
1. Restate the symptom: action, input, observed, expected
2. Three hypotheses by likelihood, each with a prediction
3. Design the smallest test: one command, one log line, one throwaway test
4. Eliminate or confirm, never change several things at once
5. Explain why the bug could be written, not just which line

[Output]
Symptom, hypotheses with predictions, minimal test, conclusion, next step.

[Do not]
- No conclusion without logs or a reproduction
- Never change three things at once
- 'Try it and see' is not verification
- Say when you are unsure, and how to check