Find the Hours You Can Call Home While Travelling
The awkward part of a long-distance call isn't the distance, it's the arithmetic — working out whether 8am your time is a reasonable hour theirs. This takes two UTC offsets and a waking window for each side, then intersects them and prints the overlap in both local times, so you propose a slot that already works for the other person. Local only; nothing leaves the tab.
- Overlap
- Two waking windows intersected, printed in both clocks
- local
- What it replaces
- Mental modulo arithmetic and one missed call
- $0.00
- Input
- Two UTC offsets and two waking windows
- no card
- Output
- Overlap hours in both local times, or a clean zero
- recomputed
What you pay otherwise
| Route | What you get | Cost |
|---|---|---|
| A world-clock app | Two clocks, and the intersection is still on you | partial |
| Someone staying up | A 5am call that neither of you enjoys | a bad call |
| Proposing a time blind | Three messages to land one slot | a day lost |
| This page | The shared hours, in both local times | $0 |
The workflow
Enter both offsets from UTC, not the city names
Offsets are what the maths needs: +2 for Central European Summer Time, -5 for US Eastern Standard. If you're unsure, a world clock shows the offset next to the city — enter that number rather than guessing the zone abbreviation.
Set a real waking window for each side
07:00–22:00 is a normal day; 06:00–23:00 is a generous one. The overlap is only as useful as the windows you enter — a 24-hour window returns a 24-hour overlap and tells you nothing.
Read the overlap in the other person's clock first
The second line of the result is their local time. Proposing in their clock is what stops the reply 'sorry, what time is that for me?' and the follow-up that costs another day.
If the overlap is zero, change a window, not the plan
A zero result is information: there is no hour that is daytime for both of you. Either someone shifts a window by an hour, or the call becomes an async message — both are better decisions than a 4am call.
Worked example
Sample: home UTC+2 (07:00-22:00), away UTC+9 (07:00-22:00) Offset gap 7 hours Overlap 2 hours Your clock 07:00-09:00 Their clock 14:00-16:00 Uploaded nothing — intersected in the tab
Numbers above are sample data produced by the tool's own pre-loaded example, run in the browser — not averages or measured benchmarks.
What breaks this
Entering city names instead of offsets gives the parser nothing to work with — it needs a number like +2 or -5. Forgetting daylight saving shifts the gap by an hour twice a year; re-check the offset after a change. Setting 24-hour waking windows returns a full-day overlap that looks useful and isn't.
Try it now
A seven-hour gap with two 07:00–22:00 windows is loaded and yields a two-hour overlap. Widen home's window to 06:00 and watch the overlap grow.
Open the overlap finder →Go deeper: the printable strip
The overlap check is free forever. The $4 one-time tier adds:
- Printable strip — both days and the overlap on one card — estimate: ~6 min saved re-checking before each call.
- Saved zones shelf — keep up to 8 zone pairs in this browser — estimate: ~8 min saved per trip of re-entering offsets.
- Slot message export — a copy-ready line with both times in it — estimate: ~4 min saved per proposal.