Utility
Timezone Overlap Calculator
Find the overlapping working hours between two time zones. Perfect for scheduling meetings with remote teams across different regions.
Select time zones and working hours
Overlap Window
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How is this calculated?
Formula: Convert working hours to UTC, find intersection.
Step 1: Convert working hours to UTC
UTC_start = local_start - offset
UTC_end = local_end - offset
Step 2: Find overlap (intersection)
overlap_start = max(UTC_start_1, UTC_start_2)
overlap_end = min(UTC_end_1, UTC_end_2)
Step 3: Calculate overlap duration
if overlap_start < overlap_end:
hours = overlap_end - overlap_start
else:
no overlap exists
Step 4: Convert back to local times
local_time = UTC_time + offset
Example: IST (9AM-5PM) vs EST (9AM-5PM)
IST in UTC: 3:30–11:30
EST in UTC: 14:00–22:00
No overlap during standard hoursCalculation history
No calculations yet.
FAQ
Frequently asked questions
How do I find overlapping working hours across time zones?
To find overlap: convert both teams' working hours to a common reference (UTC), then find the intersection. For example, EST (UTC-5) working 9 AM–5 PM = UTC 14:00–22:00. IST (UTC+5:30) working 9 AM–5 PM = UTC 3:30–11:30. Overlap in UTC: none in this case. This calculator does these conversions automatically.
What is UTC and how do time zone offsets work?
UTC (Coordinated Universal Time) is the global time reference. Time zones are expressed as offsets from UTC: EST is UTC-5 (5 hours behind), IST is UTC+5:30 (5.5 hours ahead). To convert local time to UTC, subtract the offset. To convert UTC to local, add the offset. Some zones have half-hour offsets (India +5:30, Nepal +5:45).
Do time zone offsets change with Daylight Saving Time?
Yes. Many regions shift their clocks by 1 hour during summer: EST (UTC-5) becomes EDT (UTC-4), GMT becomes BST (UTC+1), CET (UTC+1) becomes CEST (UTC+2). Not all regions observe DST — India, China, Japan, and most of Africa/Asia don't. This calculator uses standard offsets; adjust manually during DST periods.
How many hours of overlap do remote teams typically need?
Most distributed teams aim for 3-4 hours of overlap for synchronous communication (meetings, pair programming). Some fully async teams operate with zero overlap. Best practices: use the overlap window for meetings and collaborative work, handle individual tasks asynchronously. Even 2 hours of overlap can work with good async practices.
What if there is no overlap between two time zones?
When there's no overlap during standard working hours, consider: 1) Shifting one team's hours slightly earlier/later, 2) Using "relay" handoffs where one team ends their day by briefing the next, 3) Scheduling occasional meetings where one side joins early/late, 4) Going fully asynchronous with detailed documentation and recorded video updates.