Time Zone Difference Calculator
Compare offsets and time difference between IANA zones for a specific date, accounting for clock changes.
Result
Complete the fields to see the result.
The calculation runs locally in your browser.
Compare time zones by date
Choose two IANA zones and a date. The tool obtains their offsets through Intl and calculates which is ahead or behind.
Why the date matters
The difference can change during the year because regions apply different seasonal-clock rules. No fixed offsets or external APIs are used.
Frequently asked questions
Is the difference always the same?
Not necessarily. It can change when one zone changes clocks and the other does not.
What is a UTC offset?
It is a zone's difference from UTC for the selected instant.
Does this call an external service?
No. It uses time-zone information available through the browser.