Time Zone Converter

How to use it

Pick the city the time is in, then the time and the date. Every city below updates to show the same moment where they are, with the date beside it and a mark when it falls inside working hours. Add or remove cities to match whoever is involved.

Use now fills in the current time in the source city rather than yours, which is the behaviour you want when someone has just told you a time over a call. The date it fills is the date in that city too, so picking somewhere across the dateline does not start you a day out.

Everything you set goes into the page address. Copy the link and send it, and the other person opens the same comparison rather than a number they have to take on trust. For anything involving more than two people this is the whole point: one link, one shared view, no thread of corrections.

Convert on the date, not on today

This is the mistake worth avoiding. Converting a time using today's offsets and then applying the answer to a date weeks away will be an hour wrong if a clock change falls in between, and clock changes are not aligned between countries.

The United States moves on the second Sunday in March and the first Sunday in November. The United Kingdom and the European Union move on the last Sundays of March and October. For roughly two weeks in March and one in autumn, the usual gap between North America and Europe is an hour different from what everybody has memorised. The southern hemisphere runs the opposite way, so the gap between Europe and Australia moves across a three hour range over a year, and a great many countries, including India, Japan and most of Africa, never change at all.

Because this converter takes a date as well as a time, it applies the offsets that will actually be in force then. Change the date and watch a converted time move by an hour on its own: that is not a bug, it is the clock change you were about to schedule straight through.

Reading the result

Each row shows the local time, the local date, the offset from UTC and, where the browser supplies one, the zone's short name. When a city is on a different calendar date the label says so in the accent colour, because a meeting that is Tuesday for you and Wednesday for them is a meeting somebody is going to miss.

The working hours mark is deliberately blunt: it appears when the converted time is between 9am and 6pm in that city and stays away otherwise. It makes no claim about anyone's actual working pattern. It answers the question of whether you are proposing something at three in the morning for one of the people you are proposing it to, which is a question worth answering before you send the invitation rather than after.

Writing a time other people will read correctly

Once you have the answer, the way you write it decides whether it survives. A few rules that prevent nearly every avoidable mistake.

Name the zone, not the abbreviation. There are two CSTs, one in North America and one in China, and IST is claimed by India, Ireland and Israel. Write the city or the UTC offset instead.

Do not write GMT in summer. The United Kingdom is on GMT only from late October to late March; the rest of the year London is UTC+1. Writing "10am GMT" in June means either 10am or 11am in London depending on whether the writer knew that, and the reader cannot tell which.

Use the 24 hour clock, and include the date. Half the world reads 06/07 as June the seventh and the other half as the sixth of July, so write the month as a word if there is any chance of confusion. And where the exact instant matters, give a UTC time as well as a local one, because UTC is the only thing everyone can convert from without knowing where you are.

Related tools here

To see the current time in several cities rather than convert a specific one, the world clock is the board version of this, with day and night shading. To count down to a moment once it is agreed, the countdown takes a date and can be shared as a link the same way. And once the meeting is running, the timer keeps it to its length.