How does the timezone converter work?

Enter a date and time, choose your source timezone, then add one or more target timezones. The converter uses your browser's built-in Intl.DateTimeFormat API and the full IANA timezone database to calculate the exact equivalent time in each zone.

DST stands for Daylight Saving Time - the practice of advancing clocks by one hour during summer months to extend evening daylight. The "DST" badge appears when the selected date falls within the DST period for that timezone.

How do I convert EST to GMT?

Set the source timezone to "America/New_York" (EST/EDT) and add "Europe/London" (GMT/BST) as a target. EST is UTC-5; when New York observes DST (EDT), it becomes UTC-4.

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. It does not observe daylight saving time, making it a stable reference. All other timezones are expressed as offsets from UTC.

Why does the offset change at certain times of year?

Many countries observe Daylight Saving Time (DST), shifting their clocks forward in spring and back in fall. This changes their UTC offset by ±1 hour. The converter accounts for these transitions automatically using IANA timezone rules.

Timezone Converter - Convert Time Between Time Zones

How to convert time zones

Select the date and time you want to convert, choose your source timezone, and then add any number of target timezones. The results update instantly, with no button to click.

Your browser's timezone is detected automatically as the default source. You can search through the full IANA timezone database (600+ entries) by typing in the dropdown.

Understanding UTC offsets

Every timezone is defined by its offset from UTC (Coordinated Universal Time). For example:

UTC-5: US Eastern Standard Time (EST)
UTC+0: Greenwich Mean Time (GMT), which equals UTC in winter
UTC+5:30: India Standard Time (IST), a half-hour offset
UTC+9: Japan Standard Time (JST)

Daylight Saving Time (DST)

Many countries shift their clocks forward by one hour in spring and back in fall. This temporarily changes the UTC offset. A DST badge appears on any card where the selected date falls in the DST period.

Notable exceptions that never observe DST: Japan, China, India, most of Africa, and UTC itself.

Common time zone conversions

From	To UTC	Notes
EST (New York, winter)	UTC−5	Add 5 hours
EDT (New York, summer)	UTC−4	DST active
PST (Los Angeles, winter)	UTC−8	Add 8 hours
PDT (Los Angeles, summer)	UTC−7	DST active
GMT/UTC (London, winter)	UTC+0	No conversion needed
BST (London, summer)	UTC+1	DST active
CET (Paris, Berlin, winter)	UTC+1
CEST (Paris, Berlin, summer)	UTC+2	DST active
IST (India)	UTC+5:30	No DST
JST (Japan)	UTC+9	No DST
AEST (Sydney, winter)	UTC+10
AEDT (Sydney, summer)	UTC+11	DST active (southern hemisphere)

IANA timezone database

This tool uses the browser's native Intl.DateTimeFormat API, which is backed by the IANA timezone database. This database is the global standard used by operating systems and programming languages worldwide. It contains rules for every historical and future DST transition, ensuring accurate conversions even for past or future dates.

Business meeting scheduling tips

Scheduling across time zones is one of the most common use cases for this tool. Some useful reference points:

US Eastern ↔ UK: US ET is UTC−5 (winter) or UTC−4 (summer); UK is UTC+0 (winter) or UTC+1 (summer). A 2–5 PM ET slot corresponds to 7–10 PM London time in winter. The time difference narrows by 1 hour when either side observes DST.
US West Coast ↔ Asia Pacific: 8–10 AM PT (UTC−8) is late evening in Singapore (UTC+8) and Tokyo (UTC+9). Cross-Pacific calls often work better at the start of the US day or end of the Asian working day.
Finding overlap: there is typically a 1–3 hour overlap window between US East Coast business hours and Western European business hours.

International Date Line

The International Date Line runs approximately along 180° longitude (with diversions to avoid splitting island nations and territories). Crossing it from west to east subtracts one calendar day; crossing from east to west adds one day. This is why flights from the US to Asia can arrive on the same day or even the day before they departed (by clock time).

In 2011, Samoa skipped December 29–30 entirely to move to the west side of the date line, aligning with its main trading partners Australia and New Zealand.

Unix timestamp note

A Unix timestamp counts the number of seconds elapsed since 1 January 1970 00:00:00 UTC (the Unix epoch). It is timezone-independent: the same timestamp represents the same instant of time everywhere. Converting a Unix timestamp to a human-readable date always requires specifying a timezone.

This tool converts between human-readable date/times and timezones. To convert Unix timestamps, see the Unix Timestamp Converter tool.