Time Zone Converter

What Are Time Zones?

Time zones are regions of the Earth that observe a uniform standard time. The world is divided into 24 primary time zones, each roughly 15 degrees of longitude wide. Time zones are defined as offsets from Coordinated Universal Time (UTC), ranging from UTC-12 to UTC+14. Some zones use half-hour or quarter-hour offsets, such as India (UTC+5:30) and Nepal (UTC+5:45).

The concept of standardized time zones was adopted in the late 19th century to replace the thousands of local solar times used by cities and towns. Today, the IANA Time Zone Database (also called the tz database or Olson database) maintains the definitive list of all world time zones and their historical changes.

UTC Explained

UTC (Coordinated Universal Time) is the primary time standard used worldwide. It replaced Greenwich Mean Time (GMT) as the reference point for all time zones. UTC does not observe Daylight Saving Time and remains constant throughout the year. When you see a time written as "14:00 UTC", it means 2:00 PM at the prime meridian (0 degrees longitude).

All other time zones are expressed as offsets from UTC. For example, US Eastern Standard Time (EST) is UTC-5, meaning it is 5 hours behind UTC. Japan Standard Time (JST) is UTC+9, meaning it is 9 hours ahead of UTC.

How Daylight Saving Time Affects Time Zones

Daylight Saving Time (DST) shifts clocks forward by one hour during warmer months, typically to extend evening daylight. Not all countries observe DST — most of Asia, Africa, and South America do not. In the United States, DST begins on the second Sunday in March and ends on the first Sunday in November. In Europe, it runs from the last Sunday in March to the last Sunday in October.

DST can temporarily change the time difference between two cities. For example, New York and London are normally 5 hours apart, but during the brief window when the US has sprung forward but Europe has not yet, the difference shrinks to 4 hours.

Tips for Scheduling International Meetings

Find overlap: Identify the window where business hours overlap between all participants. For US East Coast and Western Europe, 9 AM–12 PM Eastern / 2–5 PM London works well.

Rotate inconvenient times: If the time gap is too large for comfortable overlap (e.g., New York and Sydney are 14–16 hours apart), rotate who takes the early or late call so the burden is shared.

Use UTC as a reference: When scheduling across 3+ time zones, specify the meeting time in UTC and let each participant convert to their local time. This eliminates confusion about which zone is the "base."

Watch for DST transitions: Around the DST changeover dates (March and November), double-check your meeting times. A recurring meeting may shift by an hour relative to participants in zones that don't observe DST.

Frequently Asked Questions

How do I convert time zones?

Select your source and target time zones from the dropdowns above and enter the time you want to convert. The tool instantly shows the equivalent time. You can also calculate manually by finding the UTC offset difference between the two zones.

What is UTC time?

UTC (Coordinated Universal Time) is the world's primary time standard. All time zones are defined as offsets from UTC. It does not observe Daylight Saving Time and remains constant year-round.

What is the time difference between New York and London?

Typically 5 hours (New York is behind). During standard time: EST (UTC-5) vs GMT (UTC+0). During DST: EDT (UTC-4) vs BST (UTC+1). The difference briefly changes to 4 or 6 hours during DST transition periods.

How do I schedule a meeting across time zones?

Find overlapping business hours using this converter. For US East Coast and Europe, 9 AM–12 PM Eastern (2–5 PM London) is the sweet spot. For wider gaps, rotate who takes the inconvenient slot.

What is Daylight Saving Time?

DST advances clocks by 1 hour during warmer months to extend evening daylight. In the US, it runs March–November. Not all countries observe it. DST can temporarily change the hour difference between two cities.