A complete reference of timezone abbreviations with UTC offsets, daylight saving time rules, and IANA zone identifiers — organized by region, with notes on the abbreviations that trip people up.

How Timezone Abbreviations Work

Timezone abbreviations are shorthand codes like EST, UTC, or JST that represent a specific UTC offset. They're used in email headers, log files, casual conversation, and display formatting. But they come with a significant catch: abbreviations are ambiguous.

The abbreviation "CST" could mean Central Standard Time (UTC-6, United States), China Standard Time (UTC+8), or Cuba Standard Time (UTC-5). "IST" could be India Standard Time (UTC+5:30), Israel Standard Time (UTC+2), or Irish Standard Time (UTC+1). Context usually resolves the ambiguity, but in data systems, "usually" isn't good enough.

This is why the IANA timezone database (also called the Olson database or tz database) exists. Instead of ambiguous abbreviations, it uses location-based identifiers like America/New_York, Asia/Kolkata, and Europe/Dublin. Each IANA zone ID maps to a specific set of historical and current UTC offset rules, including DST transitions. When precision matters, always use IANA zone IDs. Use abbreviations only for display.

Daylight Saving Time (DST) in 60 Seconds

DST is the practice of advancing clocks by one hour during warmer months so that evenings have more daylight. Not all regions observe DST — most of Asia, Africa, and South America do not. The transition dates vary by country:

United States and Canada — Spring forward on the second Sunday of March at 2:00 AM local time. Fall back on the first Sunday of November at 2:00 AM local time. Arizona (except the Navajo Nation) and Hawaii do not observe DST.

European Union — Spring forward on the last Sunday of March at 1:00 AM UTC. Fall back on the last Sunday of October at 1:00 AM UTC. The EU has debated abolishing DST but hasn't acted as of 2025.

Australia — DST varies by state. New South Wales, Victoria, Tasmania, South Australia, and ACT observe DST (October to April). Queensland, Western Australia, and Northern Territory do not.

When DST is in effect, the abbreviation changes. EST (Eastern Standard Time, UTC-5) becomes EDT (Eastern Daylight Time, UTC-4). CET (Central European Time, UTC+1) becomes CEST (Central European Summer Time, UTC+2). The underlying IANA zone ID stays the same — America/New_York covers both EST and EDT.

North America

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`EST`	Eastern Standard	UTC-5	→ EDT (UTC-4)	`America/New_York`
`EDT`	Eastern Daylight	UTC-4	Summer half	`America/New_York`
`CST`	Central Standard	UTC-6	→ CDT (UTC-5)	`America/Chicago`
`CDT`	Central Daylight	UTC-5	Summer half	`America/Chicago`
`MST`	Mountain Standard	UTC-7	→ MDT (UTC-6)	`America/Denver`
`MDT`	Mountain Daylight	UTC-6	Summer half	`America/Denver`
`PST`	Pacific Standard	UTC-8	→ PDT (UTC-7)	`America/Los_Angeles`
`PDT`	Pacific Daylight	UTC-7	Summer half	`America/Los_Angeles`
`AKST`	Alaska Standard	UTC-9	→ AKDT (UTC-8)	`America/Anchorage`
`AKDT`	Alaska Daylight	UTC-8	Summer half	`America/Anchorage`
`HST`	Hawaii Standard	UTC-10	No DST	`Pacific/Honolulu`
`AST`	Atlantic Standard	UTC-4	→ ADT (UTC-3)	`America/Halifax`
`ADT`	Atlantic Daylight	UTC-3	Summer half	`America/Halifax`
`NST`	Newfoundland Standard	UTC-3:30	→ NDT (UTC-2:30)	`America/St_Johns`
`NDT`	Newfoundland Daylight	UTC-2:30	Summer half	`America/St_Johns`

Note on Arizona: Arizona uses MST year-round (no DST), via America/Phoenix. The Navajo Nation within Arizona does observe DST.

Europe

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`GMT`	Greenwich Mean Time	UTC+0	→ BST (UTC+1)	`Europe/London`
`BST`	British Summer Time	UTC+1	Summer half	`Europe/London`
`WET`	Western European	UTC+0	→ WEST (UTC+1)	`Europe/Lisbon`
`WEST`	Western European Summer	UTC+1	Summer half	`Europe/Lisbon`
`CET`	Central European	UTC+1	→ CEST (UTC+2)	`Europe/Paris`
`CEST`	Central European Summer	UTC+2	Summer half	`Europe/Paris`
`EET`	Eastern European	UTC+2	→ EEST (UTC+3)	`Europe/Helsinki`
`EEST`	Eastern European Summer	UTC+3	Summer half	`Europe/Helsinki`
`MSK`	Moscow Time	UTC+3	No DST	`Europe/Moscow`
`TRT`	Turkey Time	UTC+3	No DST	`Europe/Istanbul`

Asia

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`IST`	India Standard Time	UTC+5:30	No DST	`Asia/Kolkata`
`PKT`	Pakistan Standard	UTC+5	No DST	`Asia/Karachi`
`NPT`	Nepal Time	UTC+5:45	No DST	`Asia/Kathmandu`
`ICT`	Indochina Time	UTC+7	No DST	`Asia/Bangkok`
`WIB`	Western Indonesia	UTC+7	No DST	`Asia/Jakarta`
`SGT`	Singapore Time	UTC+8	No DST	`Asia/Singapore`
`MYT`	Malaysia Time	UTC+8	No DST	`Asia/Kuala_Lumpur`
`HKT`	Hong Kong Time	UTC+8	No DST	`Asia/Hong_Kong`
`PHT`	Philippine Time	UTC+8	No DST	`Asia/Manila`
`KST`	Korea Standard	UTC+9	No DST	`Asia/Seoul`
`JST`	Japan Standard	UTC+9	No DST	`Asia/Tokyo`
`IRST`	Iran Standard	UTC+3:30	→ IRDT (UTC+4:30)	`Asia/Tehran`
`GST`	Gulf Standard	UTC+4	No DST	`Asia/Dubai`
`AFT`	Afghanistan Time	UTC+4:30	No DST	`Asia/Kabul`
`MMT`	Myanmar Time	UTC+6:30	No DST	`Asia/Yangon`
`BTT`	Bhutan Time	UTC+6	No DST	`Asia/Thimphu`

Note on IST ambiguity: IST is used by India (UTC+5:30), Israel (UTC+2), and Ireland (UTC+1). In data systems, always use the IANA zone ID instead: Asia/Kolkata, Asia/Jerusalem, or Europe/Dublin.

South America

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`BRT`	Brasília Time	UTC-3	No DST (since 2019)	`America/Sao_Paulo`
`ART`	Argentina Time	UTC-3	No DST	`America/Argentina/Buenos_Aires`
`CLT`	Chile Standard	UTC-4	→ CLST (UTC-3)	`America/Santiago`
`COT`	Colombia Time	UTC-5	No DST	`America/Bogota`
`PET`	Peru Time	UTC-5	No DST	`America/Lima`
`VET`	Venezuela Time	UTC-4	No DST	`America/Caracas`
`BOT`	Bolivia Time	UTC-4	No DST	`America/La_Paz`
`UYT`	Uruguay Time	UTC-3	No DST	`America/Montevideo`

Africa

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`WAT`	West Africa Time	UTC+1	No DST	`Africa/Lagos`
`CAT`	Central Africa Time	UTC+2	No DST	`Africa/Maputo`
`SAST`	South Africa Standard	UTC+2	No DST	`Africa/Johannesburg`
`EAT`	East Africa Time	UTC+3	No DST	`Africa/Nairobi`

Australia & Pacific

Abbreviation	Name	UTC Offset	DST?	IANA Zone
`AWST`	Australian Western Standard	UTC+8	No DST	`Australia/Perth`
`ACST`	Australian Central Standard	UTC+9:30	→ ACDT (UTC+10:30)	`Australia/Adelaide`
`ACDT`	Australian Central Daylight	UTC+10:30	Summer half	`Australia/Adelaide`
`AEST`	Australian Eastern Standard	UTC+10	→ AEDT (UTC+11)	`Australia/Sydney`
`AEDT`	Australian Eastern Daylight	UTC+11	Summer half	`Australia/Sydney`
`NZST`	New Zealand Standard	UTC+12	→ NZDT (UTC+13)	`Pacific/Auckland`
`NZDT`	New Zealand Daylight	UTC+13	Summer half	`Pacific/Auckland`
`FJT`	Fiji Time	UTC+12	→ FJST (UTC+13)	`Pacific/Fiji`
`ChST`	Chamorro Standard (Guam)	UTC+10	No DST	`Pacific/Guam`
`SST`	Samoa Standard	UTC-11	No DST	`Pacific/Pago_Pago`

Note on Australian DST: Queensland (Australia/Brisbane) uses AEST year-round without DST. New South Wales, Victoria, and Tasmania observe DST from the first Sunday in October to the first Sunday in April.

Universal Reference Points

Abbreviation	Name	UTC Offset	Notes
`UTC`	Coordinated Universal Time	UTC+0	The global reference. No DST. Successor to GMT for technical use.
`GMT`	Greenwich Mean Time	UTC+0	Historically the reference. Now synonymous with UTC in most contexts, but technically GMT can mean UK civil time which includes BST in summer.

The Most Ambiguous Abbreviations

These abbreviations are shared by multiple zones. If you encounter them in data, you'll need context to determine the correct one:

Abbreviation	Possible Meanings	Offsets
`CST`	Central Standard (US), China Standard, Cuba Standard	UTC-6, UTC+8, UTC-5
`IST`	India Standard, Israel Standard, Irish Standard	UTC+5:30, UTC+2, UTC+1
`BST`	British Summer, Bangladesh Standard	UTC+1, UTC+6
`PST`	Pacific Standard (US), Philippine Standard	UTC-8, UTC+8
`AST`	Atlantic Standard, Arabia Standard	UTC-4, UTC+3
`GST`	Gulf Standard, South Georgia	UTC+4, UTC-2
`ECT`	Ecuador, Eastern Caribbean	UTC-5, UTC-4

The takeaway: Always use IANA zone IDs (America/New_York, Asia/Kolkata) in code and data storage. Use abbreviations only in user-facing display where the audience context makes the meaning clear.

Related Guides

To understand how timezone offsets interact with date formats, see ISO 8601 Explained (which uses UTC offsets as timezone designators). For converting dates between timezones in bulk, see How to Convert Dates in CSV Files. For a side-by-side view of all supported date formats, see the Date Format Cheat Sheet. For a deep dive into the DST transitions that make timezone abbreviations change seasonally, see Daylight Saving Time: The Developer's Nightmare.

Timezone Abbreviations Reference