EST vs EDT and Other Time Zone Abbreviations Explained
Quick answer. EST is Eastern Standard Time, UTC−5, used on the US East Coast from November to March. In summer the East Coast is on EDT, UTC−4, and "ET" covers both. Some abbreviations have several meanings: CST is US Central Standard Time (UTC−6) or China Standard Time (UTC+8), and IST is India (UTC+5:30), Ireland or Israel. Adding the city removes the doubt.
Abbreviations like EST or IST look precise, but many of them are shared by more than one time zone. A meeting invitation that says "3 p.m. CST" can mean three different times depending on who reads it.
Abbreviations with more than one meaning
| Abbreviation | Possible meanings |
|---|---|
| CST | Central Standard Time (North America, UTC−6), China Standard Time (UTC+8), Cuba Standard Time (UTC−5) |
| IST | India Standard Time (UTC+5:30), Irish Standard Time (UTC+1, the summer time used in Ireland), Israel Standard Time (UTC+2) |
| BST | British Summer Time (UTC+1), Bangladesh Standard Time (UTC+6) |
| AST | Atlantic Standard Time (UTC−4), Arabia Standard Time (UTC+3) |
| PST | Pacific Standard Time (UTC−8), Philippine Standard Time (UTC+8) |
| MST | Mountain Standard Time (UTC−7), Malaysia Standard Time (UTC+8) |
| EST | Eastern Standard Time (UTC−5); in Australia people sometimes write EST for Australian Eastern Standard Time (UTC+10), whose proper abbreviation is AEST |
Standard time or daylight saving time?
Another trap: abbreviations differ between winter and summer. New York is EST (UTC−5) in winter and EDT (UTC−4) in summer. People often write "EST" all year, which is wrong in summer. If you write "9 a.m. EST" in July, some people will read it literally as UTC−5, an hour off from New York's actual time.
Standard and daylight pairs in common use
Most abbreviations come in pairs: one for standard time and one for daylight saving time. The table lists the pairs used in North America, Europe and Australia, with an example city for each. In the southern hemisphere the daylight saving months are reversed, so Sydney is on AEDT in January and AEST in July.
| Zone | Standard time | Daylight saving time | Example |
|---|---|---|---|
| Eastern (US, Canada) | EST, UTC−5 | EDT, UTC−4 | New York |
| Central (US, Canada) | CST, UTC−6 | CDT, UTC−5 | Chicago |
| Mountain (US, Canada) | MST, UTC−7 | MDT, UTC−6 | Denver |
| Pacific (US, Canada) | PST, UTC−8 | PDT, UTC−7 | Los Angeles |
| Alaska | AKST, UTC−9 | AKDT, UTC−8 | Anchorage |
| Hawaii | HST, UTC−10 | none | Honolulu |
| Atlantic (Canada) | AST, UTC−4 | ADT, UTC−3 | Halifax |
| Newfoundland | NST, UTC−3:30 | NDT, UTC−2:30 | St. John's |
| UK | GMT, UTC+0 | BST, UTC+1 | London |
| Western Europe | WET, UTC+0 | WEST, UTC+1 | Lisbon |
| Central Europe | CET, UTC+1 | CEST, UTC+2 | Paris |
| Eastern Europe | EET, UTC+2 | EEST, UTC+3 | Athens |
| Eastern Australia | AEST, UTC+10 | AEDT, UTC+11 | Sydney |
| Central Australia | ACST, UTC+9:30 | ACDT, UTC+10:30 | Adelaide |
| Western Australia | AWST, UTC+8 | none | Perth |
Since 2026 British Columbia, Alberta and Manitoba keep one offset all year, and each named the new time. British Columbia calls it Pacific Time, abbreviated PCT (UTC−7), from a government announcement of September 17, 2026. Alberta calls it Alberta Time, abbreviated ABT (UTC−6). Manitoba calls it Manitoba Standard Time, abbreviated MBT (UTC−5). Many phones and apps will keep showing older labels such as PDT or MST for a while, so a UTC offset is still the safest label for western Canada.
The safest ways to write a time
- Name the city: "9:00 a.m. New York time". The city carries the daylight saving rule with it.
- Give the UTC offset: "09:00 (UTC−4)". This is exact for the date.
- Use UTC itself: "13:00 UTC". Everyone can convert from it.
- Use the machine format: ISO 8601, for example 2026-10-02T09:00:00-04:00, which includes the date and offset.
- Use IANA names in software: America/New_York or Asia/Kolkata. These names include the full daylight saving history.
Why abbreviations still exist
Abbreviations are short and familiar, and in a single region they are usually understood. The problem appears when people from different countries meet. International teams are better off writing the city or UTC offset every time and letting calendar software convert the time into each person's local zone.
Any city page or Time Compare shows the UTC offset and daylight saving status for your date. Every abbreviation used on this site is listed, with its current time and a converter, in the time zone abbreviations list.
Frequently asked questions
What is the difference between EST and EDT?
EST is Eastern Standard Time (UTC−5), used in winter. EDT is Eastern Daylight Time (UTC−4), used from March to November. If you are not sure which one applies, write ET.
What does CST stand for?
Usually Central Standard Time in North America (UTC−6). The same letters are also used for China Standard Time (UTC+8) and Cuba Standard Time (UTC−5).
What does IST stand for?
India Standard Time (UTC+5:30), Irish Standard Time (UTC+1, the summer time in Ireland) or Israel Standard Time (UTC+2), depending on who is writing.
What is the clearest way to write a time zone?
Use a city name or a UTC offset, for example "15:00 London" or "15:00 UTC+1". Both mean one thing only.
Sources
- Daylight Saving Time Rules (NIST Time and Frequency Division) (checked October 26, 2026)
- No falling back with B.C.'s new time zone code, Pacific Time: PCT (BC Gov News, September 17, 2026) (checked October 26, 2026)
- Alberta's new time system (ABT) (Government of Alberta) (checked October 26, 2026)
- Manitoba's new year-round time zone: Manitoba Standard Time (MBT) (Province of Manitoba) (checked November 3, 2026)
- Time Zone Database (IANA) (checked October 26, 2026)
Keep reading
UTC Offset Explained: UTC vs GMT, and How to Convert Time
A UTC offset like UTC−5 is one number. A time zone like America/New_York is a set of rules that changes it. How to read offsets and convert between cities.
Read guide →BasicsIs Daylight Saving Time Permanent Now? Places That Stopped
Not in the US: the Senate has not passed the Sunshine Protection Act. B.C., Alberta, Manitoba and Morocco stopped changing clocks in 2026. See the full list.
Read guide →- BasicsHalf-Hour Time Zones, 45-Minute Offsets and the Date LineWhy India, Iran and Newfoundland use 30-minute offsets and Nepal 45, how UTC+14 and UTC−12 put three dates on Earth at once, and why zones follow borders.
- By regionArizona Time Zone: Same as California in Summer, Denver in WinterArizona keeps Mountain Standard Time (UTC−7) all year, so it matches Los Angeles from March to November and Denver in winter. Navajo Nation and call times.