Time Zone Converter

How do you convert between time zones?

To convert a time between zones, subtract the starting zone's UTC offset to get UTC, then add the target zone's offset. Every time zone is defined by its offset from Coordinated Universal Time (UTC), the global reference clock. Eastern Standard Time is UTC−5, which means clocks in New York read five hours earlier than UTC. India Standard Time is UTC+5:30, five and a half hours later. Once you know both offsets, any conversion takes two steps.

The two-step method

1. Convert the starting time to UTC by subtracting its offset. For a negative offset such as UTC−5, subtracting means adding 5 hours.
2. Add the offset of the target zone to the UTC time.

For example, to convert 12:00 EST to Pacific time: 12:00 + 5 hours = 17:00 UTC, then 17:00 − 8 hours = 9:00 PST. The EST to PST converter applies exactly this calculation, and the PST to EST converter runs it in reverse. Half-hour offsets work the same way: 10:00 EST is 15:00 UTC, and 15:00 + 5:30 = 20:30 IST, as the EST to IST converter shows.

If the result passes midnight, the date changes too. A time after 23:59 moves to the next day, and a time before 00:00 moves to the previous day, which is common when converting between the Americas and Asia.

GMT and UTC

For everyday scheduling, GMT and UTC show the same clock time. UTC is the precise, atomic-clock-based standard used by computers and aviation, while GMT is the name of the time zone the UK and some other countries use in winter. The UTC to EST converter is the quickest way to read a UTC timestamp in US Eastern time.

When does daylight saving time start and end?

In the United States, daylight saving time runs from the second Sunday in March to the first Sunday in November (March 8 to November 1 in 2026); in the UK and EU, summer time runs from the last Sunday in March to the last Sunday in October (March 29 to October 25 in 2026).

Daylight saving time (DST) moves clocks forward one hour in spring and back one hour in autumn. Countries switch on different dates, and some never switch at all, which is why the gap between two cities can change during the year.

• United States and most of Canada: DST starts on the second Sunday of March and ends on the first Sunday of November, with clocks changing at 2:00 a.m. local time. In 2026 that is March 8 and November 1. Hawaii and most of Arizona stay on standard time all year.
• United Kingdom and European Union: summer time starts on the last Sunday of March and ends on the last Sunday of October, with every country changing at 01:00 UTC. In 2026 that is March 29 and October 25.
• India: no daylight saving time. India Standard Time stays at UTC+5:30 all year, as do Japan and China at their own offsets.

Because the US and Europe switch on different weekends, the New York to London gap is four hours instead of five for a few weeks each year: in 2026, from March 8 to March 28 and from October 25 to October 31. US zones keep the same difference among themselves all year, so EST to PST is always three hours.

DST also changes the gap to India. The IST to EST converter shows a 10 hour 30 minute difference in winter, but while the US is on daylight time, India is 9 hours 30 minutes ahead of New York and 12 hours 30 minutes ahead of Los Angeles (see the PST to IST converter for the standard-time figure).

What is the IANA time zone database?

The IANA time zone database, also called tz or zoneinfo, is the public record of every region's UTC offset and daylight saving rules, past and present, that operating systems, browsers and programming languages use to convert times. It is maintained by a small group of volunteers and published by the Internet Assigned Numbers Authority (IANA), with new releases several times a year whenever a government changes its clocks.

Each zone is named after a representative city in the form Area/Location, not after an abbreviation: America/New_York covers US Eastern time, America/Los_Angeles covers Pacific time, Europe/London covers GMT and BST, and Asia/Kolkata covers India Standard Time. A name like America/New_York stores the full history of that region, so software can tell that 12:00 on a January date is EST (UTC−5) and 12:00 on a July date is EDT (UTC−4) without being told.

• Why not abbreviations? They are ambiguous. CST, IST and BST each mean different zones in different countries, and none of them says whether daylight saving time applies.
• Why not fixed offsets? An offset such as −05:00 is right for one moment but not for a whole year in a region that changes its clocks.
• Where it shows up: calendar apps, phone clocks, server logs and databases all rely on it, which is why an out-of-date device can show the wrong time after a rule change.

When you store or send a single moment, pair the local time with its offset in ISO 8601 form, such as 2026-09-26T12:00-04:00, or convert it to UTC. The UTC to EST converter reads UTC timestamps in US Eastern time, and the time converter handles durations such as hours and minutes.

How many time zones are there?

In theory the world has 24 one-hour zones, but more than 24 offsets are in use, because some regions keep half-hour or quarter-hour offsets and local clocks run from UTC−12 to UTC+14, a span of 26 hours. Time zones follow political borders rather than neat 15-degree slices of longitude, so each country chooses the offset that suits it.

• Half-hour offsets: India (UTC+5:30), Newfoundland in Canada (UTC−3:30) and parts of Australia such as South Australia (UTC+9:30 in winter).
• Quarter-hour offsets: Nepal (UTC+5:45) and New Zealand's Chatham Islands (UTC+12:45 in their winter).
• The extremes: Kiribati's Line Islands sit at UTC+14, the first inhabited places to start each day, while UTC−12 covers only uninhabited US islands in the Pacific.
• One zone for a wide country: China stretches across roughly 60 degrees of longitude, about four hours of solar time, but uses UTC+8 everywhere.

Because the span exceeds 24 hours, three calendar dates are in use at once for part of every day: from 10:00 to 12:00 UTC it is already tomorrow at UTC+14 and still yesterday at UTC−12. For counting days across such boundaries, the date calculators work in whole calendar days.

How do you schedule a meeting across time zones?

Name each zone by a city or a UTC offset, label recurring meetings with ET, CT or PT, and find the overlap in working hours before you pick a slot. These habits prevent most missed calls.

• Watch for duplicate abbreviations. CST can mean US Central Standard Time (UTC−6) or China Standard Time (UTC+8), and IST can mean India, Irish or Israel Standard Time. When in doubt, name a city or give the UTC offset.
• Use ET, CT and PT for year-round meetings. These generic labels mean whatever time is currently in force, standard or daylight, so an invite does not become wrong when clocks change.
• Write times in ISO 8601 with an offset. A time such as 2026-09-25T12:00-04:00 is unambiguous in any country and is how most software stores times.
• Find the overlap first. Between US Eastern and India standard time, 8:00 to 10:00 a.m. EST is 6:30 to 8:30 p.m. IST, a window that suits both sides. The GMT to IST converter helps when a UK colleague joins too.

For counting the days until a deadline or adding days to a date, use the date and calendar calculators.