Business Hours Overlap Calculator
Find the overlapping working hours between two offices in different time zones. Use it to schedule meetings, calls, or collaborative sessions without forcing either team outside normal hours.
About this calculator
When two offices operate in different time zones, only a portion of their working hours coincide. This calculator converts Office 2's hours into Office 1's local time using the UTC offset difference (offset1 − offset2), then finds the intersection of both schedules. The core formula is: overlap = max(0, min(office1_end, office2_end_in_local_time) − max(office1_start, office2_start_in_local_time)). A positive result means real shared hours exist; zero means the teams have no same-day working overlap at all. For example, a London office (UTC+0) and a Sydney office (UTC+10) with standard 9–17 schedules share very few, or zero, common hours, making asynchronous communication essential. Understanding the exact overlap window helps managers plan daily stand-ups, critical reviews, or emergency calls at times that respect both teams' working days.
How to use
Suppose Office 1 works 09:00–17:00 at UTC+0, and Office 2 works a standard 8-hour day starting at 09:00 at UTC+5. Enter office1_start = 9, office1_end = 17, office1_timezone = 0, office2_timezone = 5, office2_hours = 8. The timezone difference is 0 − 5 = −5, so Office 2's 09:00 appears as 04:00 in Office 1's time, and its end is 12:00. Overlap = max(0, min(17, 12) − max(9, 4)) = max(0, 12 − 9) = 3 hours. The two offices share 3 hours of working time each day, ideally scheduled between 09:00 and 12:00 Office 1 time.
Frequently asked questions
How do I find overlapping business hours between offices in different time zones?
Convert both offices' schedules to a single reference time zone, then find the intersection of the two windows. The overlap equals min(end1, end2_converted) − max(start1, start2_converted), floored at zero. This calculator does that conversion automatically once you enter each office's UTC offset and working hours. A result of zero means no same-day overlap exists and you will need to rely on asynchronous communication.
What happens when there is no business hours overlap between two international offices?
A zero result means the two offices' workdays do not coincide in real time, which is common between, say, a US West Coast team (UTC−8) and an India team (UTC+5:30). In that case, teams typically use asynchronous tools like email, recorded video updates, and shared project boards. Some companies introduce a rotating 'bridge shift' where one team member adjusts their schedule one or two days per week to create a short overlap window. Planning handoffs at the end of each workday ensures work continues without blocking the other team.
Why is calculating business hours overlap important for remote and distributed teams?
Without knowing the exact overlap, managers risk scheduling meetings outside normal working hours, leading to burnout, low attendance, and resentment. Even a single shared hour can be used strategically for a daily stand-up or critical decision call. Knowing the overlap window also informs hiring decisions — if collaboration is frequent, hiring closer to headquarters time zone reduces friction. Mapping overlap hours upfront is a foundational step in any remote-first team structure.