Time Zone Converter

Convert any time between two time zones. Results update instantly.

Source Time
Quick select source:
Target Timezone
Quick select target:
Source Time
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Target Time
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Enter a date and time above to see the conversion.

How to Use the Time Zone Converter

Select a date and time in the source field, then choose source and target time zones from the dropdowns. The converted time, UTC offsets, and time difference appear instantly. A DST badge appears when Daylight Saving Time is in effect for either zone on the selected date.

Understanding UTC Offsets

Every time zone is defined by its offset from Coordinated Universal Time (UTC), the world's primary time standard. UTC+0 is the baseline. New York in winter is UTC-5 (Eastern Standard Time), meaning clocks there are five hours behind UTC. Tokyo is UTC+9 (Japan Standard Time), nine hours ahead. When you convert a time, you subtract the source offset and add the target offset to find the equivalent moment.

Some offsets are not whole hours. India Standard Time (IST) sits at UTC+5:30, and Nepal Standard Time is UTC+5:45. This tool handles all fractional offsets supported by the browser's Intl API.

Daylight Saving Time (DST)

Daylight Saving Time advances clocks by one hour during summer months to shift an extra hour of daylight into the evening. In the United States, DST begins on the second Sunday in March and ends on the first Sunday in November. Most of Europe observes Summer Time from the last Sunday in March to the last Sunday in October.

Not all regions observe DST. Japan, China, India, most of the Middle East, and the majority of the Southern Hemisphere near the equator keep a fixed UTC offset year-round. When DST applies to a zone on the selected date, this calculator shows a DST badge next to the offset so you always know which offset is in effect.

How the Calculation Works

This converter uses the browser-native Intl.DateTimeFormat API, which embeds the full IANA timezone database. No external libraries are loaded. Given a date-time string, the browser resolves the correct UTC offset for that exact moment in the specified timezone, including historical DST transitions. The target time is computed by formatting the same underlying UTC timestamp in the target timezone.

Common Time Zone Conversions

Business calls between New York (EST, UTC-5) and London (GMT, UTC+0) require a five-hour difference in winter and a four-hour difference in spring/autumn because the US and Europe switch DST on different weekends. A meeting at 3 PM EST becomes 8 PM GMT. Calls from New York to Tokyo (JST, UTC+9) span fourteen hours in winter: 9 AM EST is 11 PM JST the same day.

For teams spanning the US West Coast (PST, UTC-8) and Central Europe (CET, UTC+1), the overlap is nine hours. A window of 8 AM to 11 AM PST corresponds to 5 PM to 8 PM CET, which is a practical meeting slot for both sides.

Aviation and Military Time

Aviation and the military use UTC (Zulu time) as the universal reference to avoid ambiguity. Flight schedules, weather reports, and NOTAM notices are all issued in UTC. A departure at 1400Z means 14:00 UTC regardless of where the aircraft is. This converter lets you translate Zulu times into any local timezone for situational awareness.

Quick Reference: Common Zones

The quick-select buttons at the top of the calculator cover the most frequently searched zones: Eastern Standard/Daylight Time (EST/EDT, America/New_York), Central Standard/Daylight Time (CST/CDT, America/Chicago), Pacific Standard/Daylight Time (PST/PDT, America/Los_Angeles), UTC, GMT (Etc/GMT), Central European Time/Summer Time (CET/CEST, Europe/Paris), Japan Standard Time (JST, Asia/Tokyo, always UTC+9), and India Standard Time (IST, Asia/Kolkata, always UTC+5:30). Both dropdowns also contain hundreds of IANA names grouped by region for less common zones.

FAQ

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. GMT (Greenwich Mean Time) refers to the mean solar time at the Royal Observatory in Greenwich, London. For most practical purposes they are equivalent, but UTC is the modern scientific standard. GMT is sometimes used as a time zone identifier, while UTC is the precise atomic-clock-based reference.
Daylight Saving Time is the practice of advancing clocks by one hour during warmer months so that daylight extends further into the evening. In the United States, DST runs from the second Sunday in March to the first Sunday in November. Most of Europe observes Summer Time from the last Sunday in March to the last Sunday in October. Many countries near the equator and in Asia (including Japan, China, India, and most of the Middle East) do not observe DST.
Most time zones are offset from UTC by a whole number of hours, but some countries chose offsets based on their geographic center rather than aligning to the nearest hour. India Standard Time (IST) is UTC+5:30, Nepal is UTC+5:45, and parts of Australia use UTC+9:30 or UTC+10:30. These half-hour and quarter-hour offsets are historical decisions made during a country's adoption of standardized time.
IANA timezone names (also called Olson or tz database names) are standardized identifiers like "America/New_York", "Europe/London", or "Asia/Tokyo". They are maintained by the Internet Assigned Numbers Authority and encode both the geographic location and the full history of timezone rules for that location, including past changes to DST and UTC offsets. Browsers and programming languages use these names internally.
Use this converter to find an overlap window where all participants are within normal working hours (typically 9 AM to 6 PM). A common strategy is to aim for mid-morning in the Americas (9-11 AM EST/PST), which corresponds to afternoon or early evening in Europe and early the next morning in Asia-Pacific. Rotate the inconvenient time slot between teams to share the burden fairly.