Timezone Converter
Compare a time across several zones, daylight saving handled for you
What is Timezone Converter?
A time zone converter takes a wall-clock time in one zone and shows the matching local time in as many other zones as you need, alongside the same instant as a UTC ISO 8601 string and a millisecond timestamp. It reads the IANA time zone database built into your browser, so daylight saving rules are applied automatically for the exact date you enter.
How to use Timezone Converter
- 1Choose the source time zone and enter the local time in that zone.
- 2Select the cities you want to compare against in the target list.
- 3Read the corresponding local time and UTC offset for each one.
Frequently asked questions
Why does the offset for US cities change depending on the date?+
Daylight saving time. Most of the United States and Europe move their clocks forward an hour in summer, which shifts their UTC offset. This tool reads the IANA time zone database and applies the rules in force on the specific date you entered, so a summer conversion and a winter conversion genuinely give different answers.
What format should I use for timestamps in an API?+
Either ISO 8601 with an explicit zone designator (ending in Z or +08:00, the offset for Asia/Shanghai) or a plain UTC millisecond timestamp. Sending a naive string such as "2026-07-31 10:00:00" with no zone information is the single most common source of cross-time-zone bugs.
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