Time Zone Overlap Calculator
How many working hours two locations share, and when that window opens — the arithmetic behind whether a distributed team can actually meet.
Each location has a working window in its own time.
How the time zone overlap calculator works
Each location has a working window in its own time. Shift one by the UTC offset difference and the overlap is where they intersect.
The answer is often zero, and that is the number worth knowing before hiring: two cities more than about eight hours apart share no ordinary working hours at all, which is a structural fact about the team rather than a scheduling inconvenience.
Formula: overlap = min(ends) − max(starts), in the first zone’s time
Worked examples
| Inputs | Overlapping hours | Note |
|---|---|---|
| A nine-hour difference | 0 | no overlap at all |
| A five-hour difference | 3 | three hours |
| Same zone | 8 | the full working day |
FAQFrequently asked questions
How do I find overlapping working hours?
Shift one location's working window by the time difference and take the intersection with the other. That is exactly what this does.
Why do some pairs of cities not overlap at all?
A nine- or ten-hour difference puts one side's morning in the other side's evening. Beyond about eight hours apart, two ordinary nine-to-five days stop touching entirely.
What is a workable overlap?
Three to four hours supports a normal collaborative relationship. Under two means asynchronous working with one scheduled call.
Does daylight saving change this?
Yes, and by up to two hours when the two hemispheres switch in opposite directions. Enter the offsets that apply on the date you care about.
Should someone shift their hours?
It is the usual answer, and it should be shared rather than always falling on the same side. The extended-overlap row shows what an hour each way buys.
Where these figures come from
- ISO 8601 — Date and time — Representations for information interchange — the yyyy-mm-dd format and the week-numbering rules used here
- US Naval Observatory — Calendars — the Gregorian leap-year rule
- Australian Government — public holidays — public holidays by state (not applied here)
Last checked: September 2026. The Gregorian calendar rules do not change; working-day counts exclude Saturdays and Sundays only.