Timezone Converter
Convert a date and time between IANA time zones, or find the gap between two instants.
Fill in a date, time, source and target zone.
How it works
Built entirely on the browser's own Intl.DateTimeFormat, which already ships the full IANA time zone
database — so any valid IANA zone name (America/New_York, not EST) works, and
daylight-saving transitions are read for the specific date entered rather than a fixed offset for the zone.
Why a fixed offset would be wrong
New York is UTC-5 in January and UTC-4 in July. A tool that stored one offset per zone name would get half the year wrong; reading the offset in effect at the exact wall-clock moment given is what gets a DST transition right without a separate "is this DST" check.
Example
Converting 2pm in America/New_York to Asia/Tokyo also shows the elapsed time between
"now" and that moment, so a scheduling question ("is this meeting today or tomorrow for them") and a duration
question can both be answered from one conversion.
Frequently asked questions
How does this get DST right across a transition?
It reads the target zone's actual UTC offset for the specific date and time entered, not a fixed offset for the zone — so converting a July date in New York correctly applies EDT (UTC-4) while a January date applies EST (UTC-5), without needing a separate "is this DST" check.
Why isn't my zone in the quick-pick list?
The quick-pick list is a curated set of commonly-used zones, not the full IANA database — every valid IANA zone identifier works when typed directly, the list is just a shortcut for the common ones.
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