Time Zone Converter

DateMath turns the date and time you enter into one moment on the from zone's clock, then reads that moment on every other zone's clock, with each zone's UTC offset for that exact date from the IANA time zone database in your browser. So the difference between two zones is worked out for the date you pick, never taken from a fixed table: Pacific Time is 3 hours behind Eastern Time all year, but UTC is 8 hours ahead of Pacific Time in winter and 7 in summer.

• The IANA time zone database. DateMath's time zone tools take each zone's UTC offset and daylight saving dates from the IANA time zone database (tz) built into your browser, the data computers and phones set their clocks by, so every date gets the rule in force on it. US daylight saving time runs from 2:00 AM on the second Sunday in March to 2:00 AM on the first Sunday in November (15 U.S.C. 260a); the EU and the UK change at 1:00 AM UTC on the last Sundays of March and October. Source: IANA time zones, 15 U.S.C. 260a, Directive 2000/84/EC.
• The Gregorian calendar. DateMath treats every date as a Gregorian date, with its leap-year rule: a year divisible by 4 is a leap year, except century years not divisible by 400, so 2000 had a February 29 and 2100 will not. Source: Gregorian calendar.

DateMath's date math is tested against more than 100 cases worked out by hand. Every worked example and table on the site is computed with the same code the calculators run, so a page and its calculator can't disagree.

A time zone converter answers one question: when it is this time here, what time is it there? Pick the date and the time in the zone you start from, add the zones you want, and DateMath shows the clock time in each one, its date, its UTC offset and how far ahead or behind it is. It is an online time zone converter that runs in your browser, so the result updates as you type.

The date matters because of daylight saving time. Most of the US and Canada, Europe, southeastern Australia and New Zealand move their clocks twice a year, on different dates, while UTC, India, Japan and most of Asia never do. So the difference between two zones can change during the year, and DateMath works it out for the date you pick instead of using a fixed number.

The list opens with your own time zone, read from your device, and the US zones. Up to eight zones can be compared at once, which makes the converter a quick world clock for a call or a launch; to find an hour that suits several people, use the meeting planner.

Each US time zone has two names: its standard time in winter and its daylight saving time from the second Sunday in March to the first Sunday in November. People often write EST, CST or PST all year, but in summer the clocks are on EDT, CDT and PDT, one hour later. The converter shows the name in use on your date.

EST time zone converter

Eastern Time, EST in winter (UTC−5) and EDT in summer (UTC−4), is the zone of New York, Washington and Miami. Pick Eastern Time as the from zone to convert EST to any other zone, or start from one of the most searched pairs: PST to EST, GMT to EST, IST to EST and EST to CST.

CST time zone converter: US Central Time

US Central Time is CST (UTC−6) in winter and CDT (UTC−5) in summer, for Chicago, Dallas and Houston. It is 1 hour behind Eastern Time and 2 hours ahead of Pacific Time all year. To use the converter as a US Central time zone converter, pick Central Time as the from zone. The Central pairs with their own page: EST to CST, PST to CST, UTC to CST, GMT to CST and IST to CST.

PST and PDT time zone converter

Pacific Time is PST (UTC−8) in winter and PDT (UTC−7) in summer, for Los Angeles, San Francisco and Seattle. A PDT time converts to GMT by adding 7 hours, so 9:00 AM PDT is 4:00 PM GMT; a PST time by adding 8. See PST to EST, PST to CST, PST to IST and UTC to PST.

Arizona is the exception on the mainland: most of the state stays on MST all year, so in summer Phoenix shows the same time as Los Angeles, and in winter the same time as Denver. Hawaii stays on HST all year.

The US changes its clocks at 2:00 AM local time, so each zone changes an hour after the one east of it. The EU and the UK change at 1:00 AM UTC, all at the same moment. These are the dates DateMath applies:

Between the US and the European dates the two sides are out of step: for two or three weeks in March and one week around the start of November, New York is 4 hours behind London instead of 5, and Los Angeles 7 hours instead of 8. Calendar invites move by an hour for one side in those weeks. In the southern hemisphere the seasons are the other way round: Sydney is on daylight saving time (AEDT) from October to April.

UTC, Coordinated Universal Time, is the time standard every zone is measured from: Eastern Time is UTC−5 in winter, India UTC+5:30 all year. GMT reads the same clock time as UTC and never changes, so a UTC or GMT time converts the same way. The catch is London: the UK uses GMT only in winter and BST (UTC+1) from late March to late October, so “GMT” in a summer email may mean UK time, an hour later. The list has UTC, GMT and UK time as separate zones.

UTC to IST is the same all year: add 5 hours 30 minutes. For UTC and GMT to the US zones, see UTC to PST, UTC to CST, GMT to EST and GMT to CST.

Central European Time is CET (UTC+1) in winter and CEST (UTC+2) in summer, the zone of Berlin, Paris, Madrid, Rome and Amsterdam; the converter lists it as Central European Time, Berlin. CET to EST is usually 6 hours back and CET to PST 9 hours, but in the weeks the US and Europe are out of step, both gaps are an hour smaller:

The pairs people convert most have a page of their own, with the time now in both zones, the converter set to that pair, an hour-by-hour table and the dates the difference changes. Winter is January 15, 2027 and summer July 15, 2027.

• CST means US Central Standard Time (UTC−6), but also China Standard Time (UTC+8), 14 hours apart in winter. Cuba uses CST too.
• IST is India Standard Time (UTC+5:30), and also Irish Standard Time and Israel Standard Time. The converter's IST is India.
• EST in summer almost always means Eastern Time, which is EDT then, an hour later than real EST. When it matters, ask for the city.
• BST is British Summer Time (UTC+1), not a zone of its own: it is UK time from late March to late October.

A city name avoids all of these, which is why the list names a city next to each zone.

1. Find both zones' UTC offsets on the date: Eastern is UTC−5 in winter, India UTC+5:30.
2. Subtract them: +5:30 − (−5) = 10 hours 30 minutes, so India is 10 hours 30 minutes ahead.
3. Add that to the time: 3:00 PM EST plus 10 hours 30 minutes is 1:30 AM IST, on the next day once the sum passes midnight.

The step people skip is the first: the offset on that date. Converting a July time with January offsets gives an answer one hour off, which is the most common time zone mistake. The converter always uses the date's offset. For a launch or an event set in another zone, convert its time first, then count down to it with the day countdown; to add hours to a time without a zone, use the time calculator.