Calculator Inputs
Enter two time zones, pick a reference moment, and optionally compare business-hour overlap for meetings.
Formula Used
Signed gap: Time zone gap = target UTC offset − source UTC offset.
Absolute gap: Absolute gap = |target UTC offset − source UTC offset|.
Time conversion: Target local time = source reference time + signed gap.
Overlap window: Overlap start = max(source work start in UTC, target work start in UTC).
Overlap end: Overlap end = min(source work end in UTC, target work end in UTC).
Overlap duration: Overlap minutes = max(0, overlap end − overlap start).
Because the calculator uses IANA time zones, daylight saving changes are applied automatically on the selected date.
How to Use This Calculator
- Select the source time zone where your reference time is entered.
- Select the target time zone you want to compare.
- Enter the source-zone date and time you want converted.
- Set both teams’ working-day start and end times.
- Add the meeting duration in minutes for a fit check.
- Press the calculate button to show the results above the form.
- Review the overlap window, suggested slot, and graph.
- Download the report as CSV or PDF when needed.
Example Data Table
| Source Zone | Target Zone | Reference Time | Signed Gap | Business Overlap | Suggested Meeting Slot |
|---|---|---|---|---|---|
| Asia/Karachi | America/New_York | Apr 6, 2026 6:00 PM | -9h 0m | 3h 0m | 6:30 PM - 7:30 PM Karachi |
| Europe/London | Asia/Tokyo | Apr 6, 2026 9:00 AM | +8h 0m | 1h 0m | 4:00 PM - 5:00 PM London |
| America/Los_Angeles | Australia/Sydney | Apr 6, 2026 8:00 AM | +17h 0m | 0h 0m | No centered slot available |
Frequently Asked Questions
1. What does a time zone gap mean?
A time zone gap is the signed difference between two UTC offsets at the chosen moment. It shows whether the target zone is ahead, behind, or aligned with the source zone.
2. Does this calculator account for daylight saving time?
Yes. The calculator uses named IANA time zones, so seasonal daylight saving changes are applied automatically for the selected date and time instead of using a fixed manual offset.
3. Why can the time difference change during the year?
The gap changes when one location enters or leaves daylight saving time before the other. Two cities may be eight hours apart in one month and seven in another.
4. What is the business overlap window?
It is the shared period when both locations are inside their defined work hours. This window is often the most useful range for meetings, approvals, and live collaboration.
5. Can I use it for recurring international meetings?
Yes. Test several future dates before setting a recurring meeting. This helps you catch daylight saving shifts that might make a once-convenient slot uncomfortable later.
6. What happens if a work window crosses midnight?
If the end time is earlier than the start time, the calculator treats the work window as overnight and carries the end into the next day before checking overlap.
7. Why show both signed gap and absolute gap?
The signed gap shows direction, telling you whether the target is ahead or behind. The absolute gap shows only the size of the difference, which is useful for quick comparisons.
8. Which time zone names should I choose?
Choose location-based names such as Asia/Karachi or Europe/Berlin. These names are more reliable than manual GMT offsets because they preserve location-specific daylight saving rules.