How to Convert Time Zones

To convert a time from one zone to another, you go through a common reference point: UTC. Every time zone is defined by its offset from UTC, which makes the calculation straightforward.

The method

1. Find the UTC offset for the source zone on that date.
2. Subtract it from the local time to get UTC.
3. Find the UTC offset for the destination zone on that date.
4. Add it to the UTC time.

An example

What's 3:00 PM in New York in July, in Tokyo?

• New York in July is UTC−4, so 15:00 becomes 19:00 UTC.
• Tokyo is UTC+9, so 19:00 + 9 hours = 04:00 the next day.

So 3:00 PM on Monday in New York is 4:00 AM on Tuesday in Tokyo. Don't forget to check the date as well as the time.

Common mistakes

• Ignoring daylight saving. New York is UTC−5 in winter and UTC−4 in summer. Using the wrong offset puts you an hour out.
• Assuming differences are fixed. The US and Europe change their clocks on different dates, so New York and London are 4 hours apart for a few weeks each year, not the usual 5.
• Mixing up abbreviations. "CST" can mean Central Standard Time, China Standard Time or Cuba Standard Time. Prefer city names or UTC offsets.
• Half-hour zones. India is UTC+5:30 and Nepal is UTC+5:45, so differences aren't always whole hours.

The easy way

The time zone converter applies the correct rules for the date you pick, and warns you if you pick a time that clocks skip or repeat on a change day. For a live view of several places, use the world clock.

When you schedule something with people in several zones, include the time in at least one named zone, for example "15:00 New York time", and let calendar invitations do the rest.