Time calculator
Time Zone Difference Calculator
Compare two regions using current daylight-saving-aware IANA time-zone rules.
Current offset difference
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How the time zone difference calculator works
Select two named IANA zones rather than fixed abbreviations such as EST. The browser’s Intl implementation formats the same instant in both zones and derives their current UTC offsets.
Because the calculation uses today’s instant, daylight saving is included where applicable. The difference can change during weeks when two regions switch clocks on different dates.
Worked example
On many summer dates New York is UTC−4 and London is UTC+1. The difference is +1 − (−4) = 5 hours, so London is five hours ahead. In other parts of the year the current regional rules are recalculated.
Assumptions and practical limits
This compares the current instant, not an arbitrary future meeting date. Governments can change time-zone rules, so accuracy depends on the browser’s installed zone database.
The curated list favors major zones and UTC; it is not every IANA identifier. City names represent regional rules, not travel distance.
Frequently asked questions
Does this account for daylight saving time?
Yes. Intl applies the current rules for each named IANA zone.
Why can the difference change during the year?
Regions start and end daylight saving on different dates, and some do not observe it.
Are EST and EDT separate choices?
No. Choose America/New_York so the correct seasonal abbreviation and offset are selected automatically.