How do time zones work?
The world is divided into 24 primary time zones, each roughly 15 degrees of longitude apart — the angular distance the Earth rotates in one hour. Most zones are offset from Coordinated Universal Time (UTC) by a whole number of hours, but some countries use fractional offsets: India is UTC+5:30, Nepal is UTC+5:45, and Iran is UTC+3:30. The IANA Time Zone Database (also called the tz database or zoneinfo) is the authoritative global standard for time zone definitions, maintained by the Internet Assigned Numbers Authority. It covers every historical and current time zone rule change for every region on Earth. When you convert a time using this tool, the correct UTC offset for the specific date you enter is used — meaning daylight saving time transitions are handled automatically. DST shifts clocks forward by one hour in spring and back in autumn in over 70 countries, though the exact dates vary by region.
What is UTC offset?
UTC offset is the signed difference between a specific time zone and Coordinated Universal Time (UTC), the successor to Greenwich Mean Time (GMT). For example, New York in winter is UTC−5 (Eastern Standard Time), meaning clocks there read 5 hours behind UTC. During daylight saving time it becomes UTC−4 (Eastern Daylight Time). London in winter is UTC+0 (GMT) and UTC+1 in summer (BST). Paris is UTC+1 in winter (CET) and UTC+2 in summer (CEST). The key difference between UTC and GMT is that UTC is a time standard based on atomic clocks and is never adjusted for daylight saving, while GMT is technically a time zone. In everyday use, UTC and GMT are effectively identical. This converter always uses the DST-aware UTC offset for the exact date you enter.
Frequently asked questions
What time is it in New York right now?
New York uses Eastern Time: UTC−5 in winter (EST, from the first Sunday in November to the second Sunday in March) and UTC−4 in summer (EDT). To see the current New York time, select "New York (EST/EDT)" as your target zone and convert from your local time. This converter uses DST-aware offsets so the result is always correct.
What is the difference between UTC and GMT?
UTC (Coordinated Universal Time) is the international time standard based on atomic clocks. GMT (Greenwich Mean Time) is a time zone centered on the Prime Meridian in London. In everyday use they are the same — both read UTC+0 — but technically UTC never adjusts for daylight saving time while the UK does observe BST in summer. For all practical conversion purposes, UTC and GMT are interchangeable.
How many time zones are there in the world?
There are 24 standard time zones based on 15-degree longitude bands, but the actual number of civil time zones in use worldwide is around 38–40, because many countries use non-standard half-hour or quarter-hour offsets (India UTC+5:30, Nepal UTC+5:45, Iran UTC+3:30) and some territories straddle multiple zones.
How does daylight saving time work?
Daylight saving time (DST) is the practice of advancing clocks by one hour in spring so that evenings have more daylight. Most of the United States, Canada, and Europe observe DST, but dates differ: the U.S. starts DST on the second Sunday in March and ends on the first Sunday in November. The EU transitions on the last Sunday of March and October. Countries near the equator and in Asia and Africa generally do not observe DST.
How do I convert EST to CET?
Eastern Standard Time (EST) is UTC−5. Central European Time (CET) is UTC+1. The difference is 6 hours: when it is noon EST, it is 6 PM CET. In summer, EST becomes EDT (UTC−4) and CET becomes CEST (UTC+2), so the difference remains 6 hours. Use this converter — select New York as the source and Paris or Berlin as the target — to get the exact converted time including DST adjustments.
What is the time difference between cities?
Common time differences (standard time, no DST): New York to London = 5 hours. New York to Paris = 6 hours. London to Tokyo = 9 hours. Los Angeles to New York = 3 hours. Los Angeles to London = 8 hours. These differences shift by 1 hour when one or both regions observes daylight saving time. Use this converter to get the exact difference for any specific date.
How do I convert time zones?
Enter the date and time in your source time zone, select both zones, and click Convert. The result shows the equivalent time in the target zone, accounting for daylight saving time.
What is UTC?
UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. It does not observe daylight saving time and is used as the reference point for all other time zones.