How this time zone converter works
Every timezone is defined as an offset from Coordinated Universal Time (UTC). When you convert a time from one timezone to another, the tool expresses the same instant as a different local clock reading. For example, noon UTC is 8 AM Eastern Time (UTC−4 in summer, UTC−5 in winter).
Daylight saving time (DST)
Many timezones shift their clocks by one hour in spring and back in autumn to make better use of daylight. The exact changeover dates differ by country — the United States switches on the second Sunday in March and first Sunday in November, while the European Union switches on the last Sunday in March and October.
This is why timezone abbreviations are unreliable: EST (Eastern Standard Time, UTC−5) and EDT (Eastern Daylight Time, UTC−4) both describe the same region but at different times of year. Always store and transmit times using IANA identifiers like America/New_York — they encode the full DST ruleset, not just a snapshot offset.
Common timezone abbreviations
- UTC / GMT — UTC+0, the universal reference point
- EST / EDT — Eastern US: UTC−5 (winter) / UTC−4 (summer)
- CST / CDT — Central US: UTC−6 / UTC−5
- MST / MDT — Mountain US: UTC−7 / UTC−6
- PST / PDT — Pacific US: UTC−8 / UTC−7
- CET / CEST — Central Europe: UTC+1 / UTC+2
- IST — India Standard Time: UTC+5:30 (no DST)
- CST — China Standard Time: UTC+8 (no DST)
- JST — Japan Standard Time: UTC+9 (no DST)
- AEST / AEDT — Eastern Australia: UTC+10 / UTC+11
Half-hour and quarter-hour offsets
Not all timezones are whole hours from UTC. India (UTC+5:30), Sri Lanka (UTC+5:30), Iran (UTC+3:30), and Afghanistan (UTC+4:30) use half-hour offsets. Nepal uses UTC+5:45, and the Chatham Islands use UTC+12:45. These exist for geographic or political reasons and are valid IANA timezone entries.
UTC vs. GMT
UTC (Coordinated Universal Time) and GMT (Greenwich Mean Time) share the same UTC+0 offset for most practical purposes. UTC is the modern international standard, maintained by a network of atomic clocks. GMT is a legacy designation that predates atomic timekeeping and is still used informally in many countries. Neither observes daylight saving time.
Scheduling meetings across time zones
The overlap window where business hours coincide is the main challenge for distributed teams. A few rough rules: US East Coast and Western Europe have a 1–2 hour morning overlap in winter; US West Coast and East Asia rarely share business hours at all. When scheduling, anchor the meeting time to UTC and convert to each participant's local time rather than working from one person's local clock.
Frequently asked questions
What is the time difference between New York and London?
In winter (when the US observes EST and the UK observes GMT), New York is 5 hours behind London. In summer, both regions observe daylight saving time and the difference narrows to 5 hours. However, because the US and UK switch DST dates 2–3 weeks apart, the gap briefly becomes 4 hours in spring and 6 hours in autumn.
How do I convert UTC to my local time?
Find your timezone's current UTC offset (for example, UTC−5 for US Eastern Standard Time), then add or subtract that number of hours from the UTC time. For offsets with minutes (like India's UTC+5:30), add the full hours and minutes. The converter above does this automatically — select UTC as the source timezone and your local timezone as the target.
What countries don't observe daylight saving time?
Most of Asia, Africa, and South America do not observe DST. Notable examples: China, Japan, India, and the majority of African nations stay on a fixed offset year-round. Within the United States, Arizona (except the Navajo Nation) and Hawaii don't observe DST. Russia abolished seasonal clock changes in 2014 and now stays on permanent standard time.
Why does the same abbreviation mean different time zones?
Timezone abbreviations were never standardised globally. CST means Central Standard Time (UTC−6) in North America, China Standard Time (UTC+8) in China, and Cuba Standard Time (UTC−5) in Cuba. IST is simultaneously India Standard Time (UTC+5:30), Ireland Standard Time (UTC+1), and Israel Standard Time (UTC+2). Always use IANA identifiers to avoid ambiguity.
What is UTC time?
UTC (Coordinated Universal Time) is the universal time standard that all other time zones are defined relative to. It sits at offset UTC+0 and never observes daylight saving time, making it the stable reference point for international communication, aviation, computing, and scientific work. When someone says "the meeting is at 14:00 UTC", that time means the same thing simultaneously to everyone on Earth.
How many time zones are there?
There are 24 standard time zones based on whole-hour offsets from UTC, but the real count is higher. The IANA timezone database tracks 38 distinct UTC offsets, including half-hour zones (India at UTC+5:30, Iran at UTC+3:30) and quarter-hour zones (Nepal at UTC+5:45). Counting individual IANA timezone identifiers — which track regional DST rules separately — there are over 400.
How do I convert UTC to EST, CST, or PST?
Subtract the offset from the UTC time: UTC to EST (winter) subtract 5 hours — so 15:00 UTC = 10:00 AM EST. UTC to EDT (summer) subtract 4 hours — 15:00 UTC = 11:00 AM EDT. UTC to CST subtract 6 hours; CDT subtract 5. UTC to MST subtract 7; MDT subtract 6. UTC to PST subtract 8; PDT subtract 7. The converter above handles DST automatically — select UTC as source and your target timezone.
What time is 20:00 in 12-hour format?
20:00 is 8:00 PM. To convert any 24-hour time to 12-hour format: if the hour is 12 or less it stays the same (add AM, or PM for noon); if it is 13 or above, subtract 12 and add PM. So 19:00 = 7:00 PM, 20:00 = 8:00 PM, 21:00 = 9:00 PM, 22:00 = 10:00 PM, 23:00 = 11:00 PM, 00:00 = 12:00 AM (midnight). Military time follows the same 24-hour format with no colon.
What is the IANA timezone database?
The IANA Time Zone Database (also called the tz database or zoneinfo) is the definitive global reference for timezone rules. It is maintained as an open-source project and updated several times a year when countries change their DST rules or UTC offsets. All major operating systems, programming languages, and databases ship with a copy of this database.