How to Find Overlapping Working Hours Across Time Zones

Remote teams span the globe, but real-time collaboration still needs overlapping hours. The difference between a 6-hour overlap and a 2-hour overlap completely changes how a team operates. Here’s the math for finding your window.

The formula

Overlap = max(0, min(End_A, End_B) − max(Start_A, Start_B))

Where:
  Start_A, End_A = Working hours for person A (in UTC)
  Start_B, End_B = Working hours for person B (in UTC)

Convert local times to UTC first:
  UTC time = Local time − UTC offset
  (subtract positive offsets, add negative offsets)

If the result is zero or negative, there’s no overlap — one person’s day ends before the other’s begins.

Worked example

Team member A: New York (UTC−5), works 9 AM – 5 PM local Team member B: Berlin (UTC+2), works 9 AM – 5 PM local

Convert to UTC:
  A: 9AM − (−5) = 14:00 UTC to 22:00 UTC
  B: 9AM − (+2) = 07:00 UTC to 15:00 UTC

Overlap = min(22:00, 15:00) − max(14:00, 07:00)
        = 15:00 − 14:00
        = 1 hour

That 1 hour is:
  New York: 9:00 AM – 10:00 AM
  Berlin: 3:00 PM – 4:00 PM

Three-timezone example

Add team member C: Tokyo (UTC+9), works 9 AM – 6 PM local

C in UTC: 9AM − (+9) = 00:00 UTC to 09:00 UTC

Overlap A+B+C = min(22, 15, 09) − max(14, 07, 00)
             = 9 − 14 = −5 → No overlap!

There is zero shared working time between all three.

Solution: find pairwise overlaps and schedule meetings with relevant pairs only.

Strategies for difficult time gaps

Gap size	Strategy
0–3 hours apart	Full overlap — schedule meetings freely
4–6 hours apart	2–4 hour overlap — protect it for sync meetings
7–9 hours apart	1 hour overlap — use for daily standup only
10–12 hours apart	No overlap — go fully async or shift schedules

When to calculate timezone overlap

• Planning recurring team meetings across offices
• Setting “core collaboration hours” for remote teams
• Deciding client communication windows
• Scheduling interviews with international candidates
• Planning pair programming or live code reviews

Tips for timezone management

• Agree on one “overlap window” and protect it from individual deep-work blocks
• Rotate meeting times to share the burden of early/late calls
• Define “async by default” — synchronous time is precious, use it for decisions only
• Account for Daylight Saving Time — overlaps shift by 1 hour twice a year
• Use UTC as the reference in shared calendars and documentation
• Record meetings for team members who can’t attend live
• Consider 30-minute schedule shifts: 8:30 AM instead of 9:00 AM can create an extra overlap hour

Find your team’s overlap instantly with OurDailyCalc’s timezone overlap calculator — add multiple locations and see shared working hours highlighted on a visual timeline.

TL;DR

• Overlap = min(end times) − max(start times), all in UTC
• Convert local hours to UTC before calculating
• 7+ hour gaps often mean zero practical overlap
• Protect your overlap window for synchronous decisions
• DST shifts the overlap twice a year — calendar reminders help