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Time Zones • Abbreviation Directory

Time Zone Abbreviations

Find the meaning, UTC offset, region and seasonal use of time-zone abbreviations such as EST, EDT, CST, PST, CET, BST and IST. Some abbreviations have more than one meaning, so location and date can matter.

Time-zone abbreviations are not unique identifiers. Codes such as CST, IST, BST, AST and GST can represent different time zones in different regions. For software or international scheduling, use an IANA zone or include a UTC offset when precision matters.

Best forQuick lookupHuman-readable zone labels

Watch forAmbiguityOne code can have several meanings

For softwareUse IANALocation-based civil-time rules

Find an Abbreviation Browse the Directory Time Zone Chart

Search by abbreviation, full name, UTC offset, region, country or common location.

Popular: EST EDT CST PST IST CET BST AEST

Abbreviation Resolver

Find What a Time Zone Code Means

Enter a code such as CST or IST to see every meaning listed in this directory. When a code is ambiguous, CalendarHours keeps the meanings separate instead of silently choosing one.

Abbreviation

CST

3 common meanings in this directory

→

Meaning

Multiple

Central Standard Time · China Standard Time · Cuba Standard Time

North American CST Guide See Matching Rows Convert a Time

Popular Time Zone Abbreviations

Start with the codes most often used for North American, European and international time-zone references.

UTC−05:00ESTEastern Standard Time→ UTC−04:00EDTEastern Daylight Time→ UTC−06:00CSTCentral Standard Time — context matters→ UTC−05:00CDTCentral Daylight Time→ UTC−07:00MSTMountain Standard Time→ UTC−07:00PDTPacific Daylight Time→ MultipleISTIndia / Ireland / Israel meanings→ UTC+01:00CETCentral European Time→

World Time Zone Abbreviations

Use this directory to compare code, meaning, UTC offset, seasonal usage, ambiguity and region. Duplicate codes are intentional when the same abbreviation has multiple common meanings.

Browse World Time Zones →

Showing all listed abbreviations and meanings.

Code	Meaning	UTC Offset	Usage	Ambiguity	Region	Details
ACDT	Australian Central Daylight Time	UTC+10:30	Daylight	Context recommended	Australia	Reference
ACST	Australian Central Standard Time	UTC+09:30	Standard	Context recommended	Australia	Reference
ADT	Atlantic Daylight Time	UTC−03:00	Daylight	Usually clear	North America	Reference
AEDT	Australian Eastern Daylight Time	UTC+11:00	Daylight	Usually clear	Australia	Open guide →
AEST	Australian Eastern Standard Time	UTC+10:00	Standard	Usually clear	Australia	Open guide →
AKDT	Alaska Daylight Time	UTC−08:00	Daylight	Usually clear	North America	Reference
AKST	Alaska Standard Time	UTC−09:00	Standard	Usually clear	North America	Reference
AST	Atlantic Standard Time	UTC−04:00	Standard	Multiple meanings	North America	Open guide →
AST	Arabian Standard Time	UTC+03:00	Year-round	Multiple meanings	Middle East	Open guide →
AWST	Australian Western Standard Time	UTC+08:00	Year-round	Usually clear	Australia	Reference
BJT	Beijing Time	UTC+08:00	Year-round	Context recommended	Asia	Open guide →
BRT	Brasília Time	UTC−03:00	Year-round	Context recommended	South America	Reference
BST	British Summer Time	UTC+01:00	Summer / daylight	Multiple meanings	Europe	Open guide →
BST	Bangladesh Standard Time	UTC+06:00	Year-round	Multiple meanings	Asia	Reference
BST	Bougainville Standard Time	UTC+11:00	Year-round	Multiple meanings	Pacific	Reference
CAT	Central Africa Time	UTC+02:00	Year-round	Usually clear	Africa	Reference
CDT	Central Daylight Time	UTC−05:00	Daylight	Context recommended	North America	Open guide →
CEST	Central European Summer Time	UTC+02:00	Summer / daylight	Usually clear	Europe	Open guide →
CET	Central European Time	UTC+01:00	Standard	Usually clear	Europe	Open guide →
ChST	Chamorro Standard Time	UTC+10:00	Year-round	Usually clear	Pacific	Reference
CLST	Chile Summer Time	UTC−03:00	Seasonal	Context recommended	South America	Reference
CLT	Chile Standard Time	UTC−04:00	Standard	Context recommended	South America	Open guide →
COT	Colombia Time	UTC−05:00	Year-round	Usually clear	South America	Reference
CST	Central Standard Time	UTC−06:00	Standard	Multiple meanings	North America	Open guide →
CST	China Standard Time	UTC+08:00	Year-round	Multiple meanings	Asia	Open guide →
CST	Cuba Standard Time	UTC−05:00	Standard	Multiple meanings	Caribbean	Reference
EAT	East Africa Time	UTC+03:00	Year-round	Usually clear	Africa	Reference
EDT	Eastern Daylight Time	UTC−04:00	Daylight	Usually clear	North America	Open guide →
EEST	Eastern European Summer Time	UTC+03:00	Summer / daylight	Usually clear	Europe	Open guide →
EET	Eastern European Time	UTC+02:00	Standard	Usually clear	Europe	Open guide →
EST	Eastern Standard Time	UTC−05:00	Standard	Context recommended	North America	Open guide →
FJT	Fiji Time	UTC+12:00	Civil time	Usually clear	Pacific	Reference
GMT	Greenwich Mean Time	UTC+00:00	Reference / civil	Usually clear	Global	Open guide →
GST	Gulf Standard Time	UTC+04:00	Year-round	Multiple meanings	Middle East	Open guide →
GST	South Georgia Time	UTC−02:00	Year-round	Multiple meanings	South Atlantic	Reference
HKT	Hong Kong Time	UTC+08:00	Year-round	Usually clear	Asia	Reference
HST	Hawaii Standard Time	UTC−10:00	Year-round	Usually clear	North America / Pacific	Open guide →
ICT	Indochina Time	UTC+07:00	Year-round	Usually clear	Asia	Reference
IDT	Israel Daylight Time	UTC+03:00	Daylight	Context recommended	Middle East	Reference
IRST	Iran Standard Time	UTC+03:30	Year-round	Usually clear	Middle East	Reference
IST	India Standard Time	UTC+05:30	Year-round	Multiple meanings	Asia	Open guide →
IST	Irish Standard Time	UTC+01:00	Summer / daylight	Multiple meanings	Europe	Reference
IST	Israel Standard Time	UTC+02:00	Standard	Multiple meanings	Middle East	Reference
JST	Japan Standard Time	UTC+09:00	Year-round	Usually clear	Asia	Open guide →
KST	Korea Standard Time	UTC+09:00	Year-round	Usually clear	Asia	Reference
MDT	Mountain Daylight Time	UTC−06:00	Daylight	Usually clear	North America	Open guide →
MSK	Moscow Standard Time	UTC+03:00	Year-round	Usually clear	Europe	Reference
MST	Mountain Standard Time	UTC−07:00	Standard	Context recommended	North America	Open guide →
NDT	Newfoundland Daylight Time	UTC−02:30	Daylight	Usually clear	North America	Reference
NPT	Nepal Time	UTC+05:45	Year-round	Usually clear	Asia	Reference
NST	Newfoundland Standard Time	UTC−03:30	Standard	Context recommended	North America	Open guide →
NZDT	New Zealand Daylight Time	UTC+13:00	Daylight	Usually clear	Pacific	Reference
NZST	New Zealand Standard Time	UTC+12:00	Standard	Usually clear	Pacific	Reference
PDT	Pacific Daylight Time	UTC−07:00	Daylight	Usually clear	North America	Open guide →
PET	Peru Time	UTC−05:00	Year-round	Usually clear	South America	Reference
PHT	Philippine Time	UTC+08:00	Year-round	Usually clear	Asia	Reference
PKT	Pakistan Standard Time	UTC+05:00	Year-round	Usually clear	Asia	Open guide →
PST	Pacific Standard Time	UTC−08:00	Standard	Context recommended	North America	Open guide →
SAST	South Africa Standard Time	UTC+02:00	Year-round	Usually clear	Africa	Reference
SGT	Singapore Time	UTC+08:00	Year-round	Usually clear	Asia	Reference
SST	Samoa Standard Time	UTC−11:00	Year-round	Multiple meanings	Pacific	Reference
SST	Singapore Standard Time	UTC+08:00	Year-round	Multiple meanings	Asia	Reference
TRT	Turkey Time	UTC+03:00	Year-round	Usually clear	Europe / Asia	Reference
UTC	Coordinated Universal Time	UTC+00:00	Global reference	Usually clear	Global	Open guide →
WAT	West Africa Time	UTC+01:00	Year-round	Usually clear	Africa	Reference
WEST	Western European Summer Time	UTC+01:00	Summer / daylight	Usually clear	Europe	Reference
WET	Western European Time	UTC+00:00	Standard	Usually clear	Europe	Reference
WIB	Western Indonesian Time	UTC+07:00	Year-round	Usually clear	Asia	Reference
WITA	Central Indonesian Time	UTC+08:00	Year-round	Usually clear	Asia	Reference
WIT	Eastern Indonesian Time	UTC+09:00	Year-round	Usually clear	Asia	Reference

Context Matters

Commonly Ambiguous Abbreviations

A short code can be useful in conversation while still being unsafe as a global identifier. When a code has several meanings, include the location, UTC offset or an IANA zone.

Resolve CST Resolve IST Resolve BST Resolve AST Resolve GST

CST3 meaningsUTC−06 · UTC+08 · UTC−05

IST3 meaningsUTC+05:30 · UTC+01 · UTC+02

BST3 meaningsUTC+01 · UTC+06 · UTC+11

A numeric UTC offset removes some ambiguity, while an IANA identifier is better when software must apply location-based civil-time rules across dates.

U.S. Standard & Daylight Abbreviations

Umbrella labels such as ET, CT, MT and PT can refer to different seasonal forms. Standard and daylight abbreviations have different fixed UTC offsets and should not be used interchangeably.

All U.S. Time Zones →

Umbrella Zone	Standard	Standard UTC	Daylight	Daylight UTC	Guides
Eastern Time (ET)	EST	UTC−05:00	EDT	UTC−04:00	Eastern Time →
Central Time (CT)	CST	UTC−06:00	CDT	UTC−05:00	Central Time →
Mountain Time (MT)	MST	UTC−07:00	MDT	UTC−06:00	Mountain Time →
Pacific Time (PT)	PST	UTC−08:00	PDT	UTC−07:00	Pacific Time →
Alaska Time	AKST	UTC−09:00	AKDT	UTC−08:00	Alaska →
Hawaii	HST	UTC−10:00	—	—	Hawaii →

ET vs EST vs EDT

ET means Eastern Time and acts as an umbrella label. EST is Eastern Standard Time at UTC−05:00. EDT is Eastern Daylight Time at UTC−04:00. A location that observes seasonal clock changes can use EST during one part of the year and EDT during another.

Eastern Time (ET)Eastern Standard Time (EST)Eastern Daylight Time (EDT)

CET vs CEST

CET is Central European Time at UTC+01:00. CEST is Central European Summer Time at UTC+02:00. Use the date and location to determine which seasonal form applies.

Central European Time (CET)Central European Summer Time (CEST)Convert European Time

What Does IST Mean?

IST is a classic example of why a time-zone abbreviation cannot always identify one zone by itself.

India Standard Time Guide →

UTC+05:30

India Standard Time

Used throughout India year-round. This is the dominant IST interpretation for many global and U.S.-market searches.

UTC+01:00

Irish Standard Time

Used for Ireland's summer period; Ireland's seasonal naming convention differs from the standard/daylight wording common in North America.

UTC+02:00

Israel Standard Time

The standard-time form used in Israel. Israel uses a daylight-time form on dates governed by its seasonal rules.

Abbreviation vs UTC Offset vs IANA

ESTA human-readable abbreviation. Convenient, but abbreviations can be ambiguous or seasonal.

UTC−05:00A numeric relationship to Coordinated Universal Time. Precise for an instant, but not a complete civil-time ruleset.

America/New_YorkAn IANA identifier representing location-based civil-time rules, including seasonal transitions.

When Not to Use an Abbreviation Alone

For calendar software, APIs, recurring meetings and international communication, a short code alone can be risky. Prefer an IANA identifier when the system accepts one, or include a UTC offset and location when you need a human-readable fallback.

Open Time Zone Chart Browse UTC Offsets

International Time-Zone Guides

Open dedicated references for common international abbreviations and live zone-entity clocks.

CET

Central European Time

CET, UTC+01:00, and its relationship with CEST.

Open CET → IST

India Standard Time

IST, UTC+05:30, with explicit Ireland and Israel disambiguation.

Open IST → JST

Japan Standard Time

JST, UTC+09:00, a year-round civil-time reference for Japan.

Open JST → AEST

Australian Eastern Standard Time

AEST and the seasonal relationship with AEDT where daylight time is observed.

Open AEST → EET

Eastern European Time

EET, UTC+02:00, and its summer counterpart EEST.

Open EET → GST

Gulf Standard Time

Gulf Standard Time at UTC+04:00, with ambiguity noted where GST means something else.

Open GST →

Related Time Zone Tools

Move from abbreviation lookup to chart reference, conversion, local detection or geographic exploration.

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Time Zone Chart

Compare names, abbreviations, current offsets and representative IANA zones.

Open the chart → ⇄

Time Zone Converter

Convert a specific date and clock time between zones and locations.

Convert time → ◎

What Time Zone Am I In?

Detect your IANA zone, current UTC offset and browser time-zone label.

Detect my zone → UTC

UTC Time Now

See live Coordinated Universal Time and use UTC as a global reference.

See UTC → ◉

World Time Zones

Browse time-zone references by country, region and major location.

Browse world zones → ⌖

Time Zone Map

Switch from abbreviation lookup to a geographic view of time-zone boundaries.

Open the map →

Sources & Methodology

CalendarHours treats abbreviations as display labels, not globally unique identifiers. Current local labels and offsets are derived from browser-supported IANA time-zone data, while ambiguous codes are presented with separate meanings.

Primary rulesIANA Time Zone Database

U.S. referenceNIST time & DST guidance

Browser renderingIntl.DateTimeFormat

Safety ruleDo not assume codes are unique

IANA Time Zone Database IANA — Time-Zone Naming & Abbreviation Theory NIST — Daylight Saving Time MDN — Intl.DateTimeFormat

Last reviewed: August 19, 2026. Abbreviation usage can be regional, seasonal or historical; use current IANA rules and location context when accuracy matters.

Time Zone Abbreviations FAQ

Answers to common questions about EST, EDT, CST, IST, UTC offsets and IANA identifiers.

What are time zone abbreviations?

Time-zone abbreviations are short display labels such as EST, EDT, CET or IST. They are convenient for people, but they are not always unique identifiers and may change with seasonal clock rules.

What does EST mean?

EST most commonly means Eastern Standard Time in North America. It has a fixed UTC offset of UTC−05:00. Places that observe daylight saving time may use EDT, UTC−04:00, during the daylight period instead of EST.

What is the difference between EST and EDT?

EST is Eastern Standard Time at UTC−05:00. EDT is Eastern Daylight Time at UTC−04:00. Eastern Time is an umbrella term that can refer to either seasonal form depending on the location and date.

Is ET the same as EST?

No. ET means Eastern Time, an umbrella time-zone label. EST is the standard-time form at UTC−05:00, while EDT is the daylight-time form at UTC−04:00.

What does CST mean?

CST is ambiguous. It commonly means Central Standard Time at UTC−06:00 in North America, China Standard Time at UTC+08:00, or Cuba Standard Time at UTC−05:00. Location and context are needed to know which meaning applies.

Why can CST mean different time zones?

Time-zone abbreviations were not designed as globally unique identifiers. Different regions can use the same letters for unrelated civil-time conventions, which is why an IANA identifier or numeric UTC offset is safer when precision matters.

What does IST mean?

IST has several common meanings, including India Standard Time at UTC+05:30, Irish Standard Time at UTC+01:00 during Ireland's summer period, and Israel Standard Time at UTC+02:00.

Is PST always UTC−8?

Pacific Standard Time is UTC−08:00. However, locations in the Pacific Time family that observe daylight saving time use PDT, UTC−07:00, during the daylight period. Use PT when you mean the umbrella zone rather than a fixed seasonal abbreviation.

Are time zone abbreviations unique?

No. Some are widely understood in one context, while others such as CST, IST, BST, AST and GST have multiple meanings. The abbreviation alone may not be enough to identify a civil time zone safely.

Should I use an abbreviation or an IANA time zone?

For software, calendars and international scheduling, an IANA identifier such as America/New_York or Asia/Kolkata is generally more precise because it represents location-based civil-time rules. Abbreviations are best treated as display labels.

What is the difference between a time-zone abbreviation and a UTC offset?

An abbreviation is a human-readable label such as EST. A UTC offset is a numeric difference such as UTC−05:00. Different abbreviations can share an offset, and one abbreviation can be ambiguous across regions.