Question 1

What is a timezone abbreviation?

Accepted Answer

A timezone abbreviation is a short code (usually 2–5 letters) that represents a specific timezone offset from UTC. For example, EST stands for Eastern Standard Time (UTC−5), and JST stands for Japan Standard Time (UTC+9). Abbreviations are commonly used in schedules, email headers, and broadcast media.

Question 2

What is the difference between GMT and UTC?

Accepted Answer

GMT (Greenwich Mean Time) and UTC (Coordinated Universal Time) both represent UTC+0, but they have different origins. GMT is based on the Earth's rotation as measured at the Royal Observatory in Greenwich, London. UTC is the modern atomic-clock-based standard. For everyday purposes they are interchangeable, but UTC is the official international standard used by computers and aviation.

Question 3

Why do some abbreviations like CST and BST appear twice?

Accepted Answer

Several three-letter abbreviations are shared by multiple unrelated timezones. For example, CST means Central Standard Time (UTC−6) in North America, but also China Standard Time (UTC+8). Similarly, BST means British Summer Time (UTC+1) in Europe and Bangladesh Standard Time (UTC+6) in South Asia. When communicating across regions, always clarify which timezone you mean or use the UTC offset.

Question 4

What is the difference between standard time and daylight saving time abbreviations?

Accepted Answer

Standard time abbreviations (e.g., EST, PST, CET) are used during the winter months when Daylight Saving Time is not in effect. Daylight saving time abbreviations (e.g., EDT, PDT, CEST) are used during summer months when clocks are advanced by one hour. The UTC offset is one hour more during DST.

Question 5

How do I convert between timezone abbreviations?

Accepted Answer

To convert between timezones, first find the UTC offset for each timezone. For example, EST is UTC−5 and IST is UTC+5:30, so IST is 10 hours and 30 minutes ahead of EST. You can also use the TimeandTool Timezone Converter for quick, accurate conversions between any two timezones.

Abbr	Full Name	UTC Offset	Countries / Notes	Type
EST	Eastern Standard Time	UTC-5	United States, Canada, Mexico (Quintana Roo)	STD
EDT	Eastern Daylight Time	UTC-4	United States, Canada	DST
CST	Central Standard Time	UTC-6	United States, Canada, Mexico	STD
CDT	Central Daylight Time	UTC-5	United States, Canada	DST
MST	Mountain Standard Time	UTC-7	United States, Canada, Mexico	STD
MDT	Mountain Daylight Time	UTC-6	United States, Canada	DST
PST	Pacific Standard Time	UTC-8	United States, Canada	STD
PDT	Pacific Daylight Time	UTC-7	United States, Canada	DST
AKST	Alaska Standard Time	UTC-9	United States	STD
AKDT	Alaska Daylight Time	UTC-8	United States	DST
HST	Hawaii–Aleutian Standard Time	UTC-10	United States	STD
AST	Atlantic Standard Time	UTC-4	Canada, Caribbean islands	STD
NST	Newfoundland Standard Time	UTC-3:30	Canada	STD
BRT	Brasilia Time	UTC-3	Brazil	STD
ART	Argentina Time	UTC-3	Argentina	STD
CLT	Chile Standard Time	UTC-4	Chile	STD
CLST	Chile Summer Time	UTC-3	Chile	DST
PET	Peru Time	UTC-5	Peru	STD
COT	Colombia Time	UTC-5	Colombia	STD

Abbr	Full Name	UTC Offset	Countries / Notes	Type
GMT	Greenwich Mean Time	UTC+0	United Kingdom, Ireland, Portugal +1 more	STD
UTC	Coordinated Universal Time	UTC+0	International standard	STD
BST	British Summer Time	UTC+1	United Kingdom	DST
CET	Central European Time	UTC+1	France, Germany, Italy +8 more	STD
CEST	Central European Summer Time	UTC+2	France, Germany, Italy +8 more	DST
EET	Eastern European Time	UTC+2	Finland, Greece, Romania +5 more	STD
EEST	Eastern European Summer Time	UTC+3	Finland, Greece, Romania +5 more	DST
WET	Western European Time	UTC+0	Portugal, Canary Islands (Spain), Morocco (in winter)	STD
WEST	Western European Summer Time	UTC+1	Portugal, Canary Islands (Spain)	DST
MSK	Moscow Standard Time	UTC+3	Russia	STD

Abbr	Full Name	UTC Offset	Countries / Notes	Type
IST	India Standard Time	UTC+5:30	India, Sri Lanka	STD
JST	Japan Standard Time	UTC+9	Japan	STD
KST	Korea Standard Time	UTC+9	South Korea, North Korea	STD
CST	China Standard Time	UTC+8	China, Taiwan	STD
HKT	Hong Kong Time	UTC+8	Hong Kong	STD
SGT	Singapore Time	UTC+8	Singapore	STD
AEST	Australian Eastern Standard Time	UTC+10	Australia	STD
AEDT	Australian Eastern Daylight Time	UTC+11	Australia	DST
NZST	New Zealand Standard Time	UTC+12	New Zealand	STD
NZDT	New Zealand Daylight Time	UTC+13	New Zealand	DST
PKT	Pakistan Standard Time	UTC+5	Pakistan	STD
NPT	Nepal Time	UTC+5:45	Nepal	STD
BST	Bangladesh Standard Time	UTC+6	Bangladesh	STD
ICT	Indochina Time	UTC+7	Thailand, Vietnam, Cambodia +1 more	STD
WIB	Western Indonesian Time	UTC+7	Indonesia	STD
WITA	Central Indonesian Time	UTC+8	Indonesia	STD
WIT	Eastern Indonesian Time	UTC+9	Indonesia	STD
GST	Gulf Standard Time	UTC+4	United Arab Emirates, Oman	STD

Abbr	Full Name	UTC Offset	Countries / Notes	Type
EAT	East Africa Time	UTC+3	Kenya, Tanzania, Uganda +4 more	STD
CAT	Central Africa Time	UTC+2	Zimbabwe, Zambia, Malawi +3 more	STD
WAT	West Africa Time	UTC+1	Nigeria, Cameroon, Niger +4 more	STD
SAST	South Africa Standard Time	UTC+2	South Africa, Lesotho, Swaziland	STD

Timezone Abbreviations — Complete Reference Guide

Americas

Europe

Asia-Pacific

Africa / Middle East

Timezone Tools

Frequently Asked Questions about Timezone Abbreviations