Time Zone Converter

Convert times across world time zones instantly. Compare EST, PST, GMT, JST, KST, and more with automatic daylight saving adjustments. Free online time zone converter.

Select a date for DST determination

Enter in 24-hour format

How to Use

  1. Select the source time zone

    Choose the time zone of the time you want to convert from.

  2. Enter the time

    Input the time you want to convert.

  3. Select the target time zone

    Choose the destination time zone to see the converted time instantly.

What is time zone conversion?

Time zone conversion is the calculation that turns the local time in one region into the local time in another. Every time zone is defined by its offset — how far it sits from UTC (Coordinated Universal Time). Seoul is UTC+9, while New York is UTC-5 (or -4 during daylight saving time). The gap between two cities is exactly the difference between their offsets.

Why it is not simple addition

  • Daylight saving time (DST) — the US and Europe move clocks forward by one hour from spring to autumn, so the gap for the same city shifts with the season.
  • 30- and 45-minute offsets — some places, such as India (UTC+5:30) and Nepal (UTC+5:45), are not on a whole-hour offset.
  • Date rollover — when the result crosses midnight, the date moves a day forward or back.

This tool uses the IANA time zone database, so DST for the chosen date is applied automatically. It is handy for video calls, flight arrival times, and overseas deadlines.

The formula

First convert the source time to UTC, then add the target zone's offset.

UTC = source local time - source offset

target local time = UTC + target offset

difference = (target offset - source offset) ÷ 60 (minutes to hours)

Example — converting June 3, 15:00 in Seoul (UTC+9, +540 min) to New York (EDT, UTC-4, -240 min):
UTC = 15:00 - 9 hours = 06:00
New York = 06:00 + (-4 hours) = 02:00
difference = (-240 - 540) ÷ 60 = -13 hours (New York is 13 hours behind). Midnight is not crossed, so the date stays June 3.

Frequently Asked Questions

What is a time zone?
A time zone is the standard time for a region of the world divided along lines of longitude. Each zone has an offset from UTC (Coordinated Universal Time). Korea Standard Time (KST) is UTC+9 and US Eastern Standard Time (EST) is UTC-5, and roughly 38 distinct offsets exist worldwide.
How are UTC and GMT different?
UTC (Coordinated Universal Time) is the standard reference for all time zone calculations, measured precisely with atomic clocks. GMT (Greenwich Mean Time) is the astronomical time at the Greenwich Observatory in Britain; it is almost identical to UTC, though strictly speaking UTC is the more precise standard. For everyday use you can treat them as the same.
Is daylight saving time (DST) taken into account?
Yes. Based on the date you enter, the IANA time zone data automatically determines whether DST applies in each zone. That is why the gap for the same city can differ between June and December.
What is daylight saving time (DST)?
DST is the practice of moving clocks forward by one hour in summer to make better use of daylight. The US, Europe and others start in spring and end in autumn, and during this period the UTC offset gains an extra hour. Korea and Japan do not currently observe DST.
What is the time difference between Korea and the US?
Korea (KST) is 14 hours ahead of the US East Coast (EST) and 17 hours ahead of the West Coast (PST). During US daylight saving time (roughly March to November) the gap shrinks by one hour to 13 hours for the East and 16 hours for the West.
Why does the date change in the result?
When the difference between two regions is large enough that the converted time crosses midnight, the date shifts a day forward or back. For example, 9 AM in Seoul becomes 4 PM the previous day in Los Angeles (during DST), so the date moves a day earlier.
Are 30- or 45-minute differences calculated too?
Yes. Offsets that are not whole hours, such as India (UTC+5:30), Nepal (UTC+5:45) and parts of Australia (UTC+9:30), are calculated precisely down to the minute.
Can I compare several time zones at once?
Yes. Enter a time in a source zone and you can see the converted time, the difference and both UTC offsets for the target zone at a glance.
2026 calendar data

Related Calculators

Date Calculator날짜 차이(일)Days Between Dates날짜 차이(일/평일)Day of WeekDate.getDay() → 요일 매핑Time Duration종료시간 - 시작시간 (자정 넘김 시 +24h)