How to convert time zones

The fastest way to convert a time is to let a clock do it. Open the world clock, add the cities you care about, and pick a time in one of them. TimeZonar shows the same moment in every other city, with daylight saving already taken into account.

It still helps to know how to do it by hand: to check an answer, to work out a time on paper, or to spot when a meeting invite looks wrong. It only takes three steps.

• 1. Find each place's offset on that date. The offset is how far the place is from UTC. Look it up for the day you care about, not today, because daylight saving time can change it.
• 2. Turn the starting time into UTC. Subtract the starting place's offset. For a negative offset like UTC−7, subtracting means adding 7 hours.^[1]
• 3. Turn UTC into the other place's time. Add the other place's offset.

Using a 24-hour clock while you work avoids AM and PM mistakes. Convert back to AM and PM at the end if you need to.

What time is 9:00 AM in Los Angeles on March 20, 2026, in Berlin?

• Offsets. Los Angeles moved its clocks forward on March 8, so it's on UTC−7.^[2] Berlin doesn't change until March 29, so it's still on UTC+1.^[3]
• To UTC. 09:00 minus −7 hours is 09:00 plus 7 hours: 16:00 UTC.
• To Berlin. 16:00 plus 1 hour is 17:00, or 5:00 PM on March 20.

A month later, on April 20, Berlin is on summer time too (UTC+2), and the same 9:00 AM in Los Angeles is 6:00 PM in Berlin. The two cities are usually nine hours apart, but for those few weeks in March the gap is eight. That's the kind of change that catches people out, and it's why step 1 says "on that date".

If you only need the difference between two places, subtract one offset from the other. In the example above, Berlin's UTC+1 minus Los Angeles's UTC−7 is +8, so Berlin is 8 hours ahead. Add 8 hours to any Los Angeles time to get Berlin time on that date.

The same idea works for half-hour and quarter-hour offsets. At 10:00 in London in January (UTC+0), it's 15:30 in Mumbai (UTC+5:30) and 20:30 in Adelaide, which is on summer time at UTC+10:30.

If your answer goes past 24:00, it's the next day. If it goes below 00:00, it's the day before. For example, 6:00 PM on Thursday in New York in January (UTC−5) is 23:00 UTC, and adding Tokyo's 9 hours gives 32:00. Take away 24 and you get 08:00 on Friday in Tokyo.

Always write the date next to the converted time when you send it to someone. "8 AM Friday Tokyo time" is much harder to get wrong than "8 AM".

• Using today's offset for a future date. If the date is on the other side of a clock change, the offset will be different. See daylight saving time for when clocks change.
• Trusting abbreviations. CST means one thing in North America and another in China, and IST can mean India, Ireland or Israel.^[4] Name a city instead, like "3 PM Chicago time".
• Assuming neighbors share rules. Phoenix and Denver are both on Mountain Time, but Phoenix doesn't use daylight saving time. In winter they show the same time; in summer, Denver is an hour ahead.
• Forgetting the date. A late-evening time in the Americas is often the next morning in Asia and Australia.

To find a time that works for several people at once, read scheduling across time zones. For the background on offsets and why they change, read how time zones work.

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 changing on the second Sunday in March.
3. 3.EUR-Lex, Directive 2000/84/EC on summer-time arrangements. EU clocks changing on the last Sunday in March.
4. 4.IANA, Theory and pragmatics of the tz code and data. Why abbreviations like CST and IST are ambiguous, and naming zones by place instead.