Remote Work Timezone Overlap Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
Timezone overlap is calculated by shifting B's hours into A's timezone (B's hour − offset), then taking the intersection of the two work windows. For a -9h offset and identical 9am-5pm hours, the overlap is 0 hours.
Explanation
Working with colleagues in a different time zone requires knowing precisely how many hours the two work schedules actually coincide, to plan meetings or synchronous work sessions without guessing. This calculator first shifts person B's hours into person A's timezone (by subtracting the time zone offset), then calculates the intersection between the two now-aligned work windows — exactly the same math as an interval intersection. A result of zero hours doesn't mean a calculation error: for very distant time zones (for example France and California, a 9-hour gap), standard office hours (9am-5pm) on both sides simply don't overlap at all, a reality well known to teams spread across these two regions, who then have to deliberately shift their hours or accept meetings outside their usual working time. This calculator is deliberately limited to working hours within the same calendar day, without handling cases where the shifted window crosses midnight: for converting one specific point in time rather than intersecting two windows, see our time zone converter.
Example: a 3-hour offset, 9am-5pm hours on both sides
Inputs
Offset: +3h. A's hours: 9am-5pm. B's hours: 9am-5pm.
Calculation
B's hours shifted into A's timezone: 9−3=6am to 17−3=2pm. Overlap = max(0, min(17,14) − max(9,6)) = max(0, 14−9) = 5h.
Result
The two people share 5 hours of common working time each day.
Frequently asked questions
Why could the result be zero hours?
Because for two very distant time zones (for example an 8 to 12 hour gap), standard office hours on both sides simply don't overlap within the same day at all. This is a correct, expected result, not a calculation error: the teams involved then need to deliberately shift part of their schedule or accept meetings outside one side's usual hours.
How do I know the exact time difference between two cities?
The offset between two time zones sometimes varies depending on the time of year because of daylight saving time, which isn't applied on the same dates everywhere in the world (and not at all in some countries). Check the current offset at the specific time you care about rather than relying on a memorized value, especially around spring and autumn clock changes.
Does this calculator handle cases where the shifted hours cross midnight?
No, this calculator is deliberately limited to working hours contained within the same calendar day once shifted into the same timezone reference. For an extreme offset combined with atypical working hours (night shifts, for example), a zero or unexpected result may simply reflect this limitation, rather than a genuine absence of overlap at some other point in the day.
How do I plan a one-off meeting rather than a recurring overlap?
This calculator gives the number of regular common working hours between two people, day after day. To check the exact time of a one-off event in the other person's timezone (or calculate how many days remain before that meeting), see our date difference calculator.