Time zone converter

Every conversion is the same three steps, and they're the three lines of "The working" above:

• Find each place's offset on that date. The offset is how far its clocks are from UTC. Look it up for the day you're converting, not today, because daylight saving time changes it.
• Subtract the starting offset to get UTC. 9:00 in New York in winter (UTC−5) is 9:00 − (−5 h) = 14:00 UTC. Subtracting a negative offset means adding.^[1]
• Add the other place's offset. 14:00 UTC in Tokyo (UTC+9) is 23:00. If the sum passes midnight, it's the next day; if it drops below zero, the day before.

For more worked examples and the mistakes people make most often, read how to convert time zones.

These tables are worked out in your browser for today, so they're right whatever the season.

A place's offset isn't a fixed number. It's whatever its government's rules say for that date, and two kinds of change move it:

• Daylight saving time moves the clocks forward an hour in spring and back in autumn, so New York is UTC−5 in winter and UTC−4 in summer.^[2]
• Rule changes happen when a government decides. Mexico stopped using daylight saving time in 2022, and Kazakhstan moved the whole country to UTC+5 in 2024.^{[6, 7]} Changes like these are recorded in the IANA time zone database, which phones, computers and this converter all rely on.^[5]

That's why the converter asks for a date as well as a time, and why the same two cities can be a different number of hours apart in March than in January. For the full picture, read how time zones work, or look up any zone in the list of time zones.

Places that use daylight saving time change on their own dates:

• United States: forward on the second Sunday in March, back on the first Sunday in November, at 2:00 AM local time.^[2]
• United Kingdom: forward at 1:00 AM on the last Sunday in March, back at 2:00 AM on the last Sunday in October.^[4]
• European Union: the last Sundays in March and October, at 01:00 UTC in every country at once.^[8]
• Australia (where used): forward on the first Sunday in October, back on the first Sunday in April. New Zealand: forward on the last Sunday in September, back on the first Sunday in April.^{[9, 10]}

On a change night, one local hour is skipped in spring and one is repeated in autumn. If you enter a skipped time, like 2:30 AM in New York on the spring change, the converter reads it with the offset from before the jump, giving 3:30 AM. If you enter a repeated time, it uses the first one. That's how calendar software reads these times too, so the converter agrees with your calendar.^[11]

The dates, and which countries take part, are in the daylight saving time guide.

Under the hood, this converter does what your code should: it names places by IANA zone ID, like America/New_York, and lets the time zone database work out the offset for each date. Abbreviations such as CST or IST can mean different zones in different countries, so don't store them.^[12]

// JavaScript, in any modern browser or Node
new Intl.DateTimeFormat("en-GB", {
  timeZone: "Europe/London",
  timeStyle: "short",
}).format(new Date("2026-01-15T14:00:00Z"));
// "14:00"

# Python 3.9+
from datetime import datetime
from zoneinfo import ZoneInfo
datetime(2026, 1, 15, 9, 0, tzinfo=ZoneInfo("America/New_York")) \
    .astimezone(ZoneInfo("Europe/London"))
# 2026-01-15 14:00:00+00:00

Python's zoneinfo needs time zone data from the operating system or the tzdata package.^[13] For storing times, handling skipped hours and testing, read programming with time zones and the IANA time zone database resource.

• Live world clock and map

  The home page: your own time next to up to eight cities, on a live day and night map.

• Meeting planner

  Find the best meeting time for up to 10 places, scored hour by hour, with daylight saving handled.

• Meeting cost calculator

  Work out what a meeting costs in people's time, per meeting and per year, from salaries or hourly rates.

• World clock

  The time right now in every UTC offset in use, west to east, with your own cities pinned on top.

• UTC offset calculator

  Find the UTC offset of any place on any date, or every place on an offset, in every notation.

• DST change tracker

  Every clock change worldwide in the next 12 months, your places' next change, and when two places' gap shifts.

1. 1.IETF, RFC 3339: Date and Time on the Internet: Timestamps. An offset is local time minus UTC, so subtracting it gives UTC.
2. 2.U.S. Department of Transportation, Daylight Saving Time. US clocks all changing on the same dates, at 2:00 a.m. local time.
3. 3.NIST, How is UTC(NIST) related to UTC, TAI, GMT, GPS time and Zulu time?. GMT as today's name for the time zone at 0°, the same time as UTC.
4. 4.GOV.UK, When do the clocks change?. UK change dates, and British Summer Time.
5. 5.IANA, Time Zone Database. The shared record of every place's offsets and rule changes, updated when governments change them.
6. 6.Bloomberg Línea, Mexico abolishes daylight saving time. Mexico ending daylight saving in 2022.
7. 7.Interfax, Kazakhstan to switch to single time zone. Kazakhstan moving to UTC+5 on March 1, 2024.
8. 8.EUR-Lex, Directive 2000/84/EC on summer-time arrangements. EU change dates, all at 01:00 UTC.
9. 9.NSW Communities and Justice, Daylight saving. Australian change dates.
10. 10.New Zealand Government, Daylight saving. New Zealand change dates.
11. 11.IETF, RFC 5545: Internet Calendaring and Scheduling (iCalendar). How calendars read skipped and repeated local times.
12. 12.IANA, Theory and pragmatics of the tz code and data. Area/Location zone names, and why abbreviations like CST and IST are ambiguous.
13. 13.Python documentation, zoneinfo: IANA time zone support. Converting with IANA zones in Python.