Advanced options
Assumes both sides work the same clock hours locally. Examples from the UK: Central Europe +1, India +5.5, Singapore +8 (hours ahead), US East Coast 5 behind, West Coast 8 behind, varying with the daylight-saving dance in spring and autumn when the gap shifts by an hour for a few weeks.
What The Time Zone Overlap Calculator Works Out
- Working-hours overlap: two working days of the same length separated by d hours share (day length minus d) hours of mutual office time. The UK and Central Europe live in near-total overlap, the UK and the US East Coast share a workable 3 hours, the UK and India a tight 2.5, and the UK with California or Singapore precisely nothing.
- Verdict: 5 or more shared hours is comfortable, 3 to 5 workable with discipline, under 3 means the window is for decisions only, and zero means a relay model: handover documents and follow-the-sun support rather than meetings.
- Common examples: the standard UK pairings at a 9 to 5 both ends. The American and European clock changes fall on different Sundays, so every gap wobbles by an hour for a few weeks each spring and autumn.
- The other team is ahead or behind (advanced): the direction decides whether the shared window falls in your morning (they are ahead, so their afternoon is your morning) or your afternoon (they are behind). It does not change the number of hours, only when they are.
- Start times and their day length (advanced): set each side's real start hour and the other team's day length, for teams that work 8 to 4, 10 to 7 or longer flexible days. Half hours work for India (+5.5).
- Shared window in both clocks (advanced): the overlap as clock times at each end, which is what actually goes in the calendar invitation.
- Best meeting slot (advanced): the middle of the shared window, fair to both ends. A fixed meeting time exports its pain to the same time zone forever, so mature distributed teams rotate the inconvenient slot and treat the 6am or 11pm call as a cost to budget, not a loyalty test.
- Overlap if you flex (advanced): how many extra shared hours you buy by starting your day earlier (for a team ahead of you) or later (for one behind). An hour of flex at one end is often the difference between no overlap and a daily standup.
- Hour-by-hour table (advanced): every hour across both working days showing who is at work, for spotting the slots where only one side is in and async handovers should land.