1. Scope
Finds working-hour overlap between two or more teams in different time zones and surfaces daylight-saving-time pivots. Not a scheduling engine — output is informational.
2. Inputs and outputs
Inputs
- timezones array
Each: IANA zone, working-hours window.
Outputs
- overlapWindows
UTC ranges with overlap across all members.
- dstWarnings
Dates where DST changes shift the overlap window.
Engine source: src/lib/time-zone-overlap-planner/engine.ts
3. Formula / scoring logic
for each UTC hour h in [0..23]:
if h is inside every member's local working hours → overlap
4. Assumptions
- Working hours are entered in local time per member.
- Uses IANA time zone database via the browser's Intl API — subject to the browser's bundled TZDB version.
5. Data sources
- IANA Time Zone Database as of 2024b
6. Known limitations
- Cross-hemisphere DST offsets (e.g. US fall-back vs EU fall-back 1 week apart) can temporarily narrow or widen the overlap — the tool surfaces the warning but does not auto-reschedule.
7. Reproducibility
Input
members = [Berlin 9–17, NYC 9–17].
Expected output
overlap ≈ 15:00–17:00 Berlin / 09:00–11:00 NYC (standard time); DST warning active for the two weeks each spring/fall when offsets diverge.
8. Change log
- 2026-04-24 methodology page first published.