Timezone acronyms and abbreviations

A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. It is convenient for areas in close commercial or other communication to keep the same time, so time zones tend to follow the boundaries of countries and their subdivisions.

Most of the time zones on land are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12 to UTC+14), but a few are offset by 30 or 45 minutes. Some higher latitude countries use daylight saving time for part of the year, typically by changing clocks by an hour. Many land time zones are skewed toward the west of the corresponding nautical time zones. This also creates a permanent daylight saving time effect.

Alphabetically sorted. Note that some of the abbreviations are not unique, these will have several entries in the list. Other time zones have many common names, and each of these will be listed as well.

Abbreviation Full name Location Time zone
A Alpha Time Zone Military UTC + 1 hour
ACDT Australian Central Daylight Time Australia UTC + 10:30 hours
ACST Australian Central Standard Time Australia UTC + 9:30 hours
ADT Atlantic Daylight Time North America UTC – 3 hours
AEDT Australian Eastern Dayl. Time or Australian Eastern Summer Time Australia UTC + 11 hours
AEST Australian Eastern Standard Time Australia UTC + 10 hours
AKDT Alaska Daylight Time North America UTC – 8 hours
AKST Alaska Standard Time North America UTC – 9 hours
AST Atlantic Standard Time North America UTC – 4 hours
AWDT Australian Western Daylight Time Australia UTC + 9 hours
AWST Australian Western Standard Time Australia UTC + 8 hours
B Bravo Time Zone Military UTC + 2 hours
BST British Summer Time Europe UTC + 1 hour
C Charlie Time Zone Military UTC + 3 hours
CDT Central Daylight Time Australia UTC + 10:30 hours
CDT Central Daylight Time North America UTC – 5 hours
CEDT Central European Daylight Time Europe UTC + 2 hours
CEST Central European Summer Time Europe UTC + 2 hours
CET Central European Time Europe UTC + 1 hour
CST Central Summer Time Australia UTC + 10:30 hours
CST Central Standard Time Australia UTC + 9:30 hours
CST Central Standard Time North America UTC – 6 hours
CXT Christmas Island Time Australia UTC + 7 hours
D Delta Time Zone Military UTC + 4 hours
E Echo Time Zone Military UTC + 5 hours
EDT Eastern Daylight Time Australia UTC + 11 hours
EDT Eastern Daylight Time North America UTC – 4 hours
EEDT Eastern European Daylight Time Europe UTC + 3 hours
EEST Eastern European Summer Time Europe UTC + 3 hours
EET Eastern European Time Europe UTC + 2 hours
EST Eastern Summer Time Australia UTC + 11 hours
EST Eastern Standard Time Australia UTC + 10 hours
EST Eastern Standard Time North America UTC – 5 hours
F Foxtrot Time Zone Military UTC + 6 hours
G Golf Time Zone Military UTC + 7 hours
GMT Greenwich Mean Time Europe UTC
H Hotel Time Zone Military UTC + 8 hours
HAA Heure Avancée de l’Atlantique North America UTC – 3 hours
HAC Heure Avancée du Centre North America UTC – 5 hours
HADT Hawaii-Aleutian Daylight Time North America UTC – 9 hours
HAE Heure Avancée de l’Est North America UTC – 4 hours
HAP Heure Avancée du Pacifique North America UTC – 7 hours
HAR Heure Avancée des Rocheuses North America UTC – 6 hours
HAST Hawaii-Aleutian Standard Time North America UTC – 10 hours
HAT Heure Avancée de Terre-Neuve North America UTC – 2:30 hours
HAY Heure Avancée du Yukon North America UTC – 8 hours
HNA Heure Normale de l’Atlantique North America UTC – 4 hours
HNC Heure Normale du Centre North America UTC – 6 hours
HNE Heure Normale de l’Est North America UTC – 5 hours
HNP Heure Normale du Pacifique North America UTC – 8 hours
HNR Heure Normale des Rocheuses North America UTC – 7 hours
HNT Heure Normale de Terre-Neuve North America UTC – 3:30 hours
HNY Heure Normale du Yukon North America UTC – 9 hours
I India Time Zone Military UTC + 9 hours
IST Irish Summer Time Europe UTC + 1 hour
K Kilo Time Zone Military UTC + 10 hours
L Lima Time Zone Military UTC + 11 hours
M Mike Time Zone Military UTC + 12 hours
MDT Mountain Daylight Time North America UTC – 6 hours
MESZ Mitteleuroäische Sommerzeit Europe UTC + 2 hours
MEZ Mitteleuropäische Zeit Europe UTC + 1 hour
MSD Moscow Daylight Time Europe UTC + 4 hours
MSK Moscow Standard Time Europe UTC + 3 hours
MST Mountain Standard Time North America UTC – 7 hours
N November Time Zone Military UTC – 1 hour
NDT Newfoundland Daylight Time North America UTC – 2:30 hours
NFT Norfolk (Island) Time Australia UTC + 11:30 hours
NST Newfoundland Standard Time North America UTC – 3:30 hours
O Oscar Time Zone Military UTC – 2 hours
P Papa Time Zone Military UTC – 3 hours
PDT Pacific Daylight Time North America UTC – 7 hours
PST Pacific Standard Time North America UTC – 8 hours
Q Quebec Time Zone Military UTC – 4 hours
R Romeo Time Zone Military UTC – 5 hours
S Sierra Time Zone Military UTC – 6 hours
T Tango Time Zone Military UTC – 7 hours
U Uniform Time Zone Military UTC – 8 hours
UTC Coordinated Universal Time Europe UTC
V Victor Time Zone Military UTC – 9 hours
W Whiskey Time Zone Military UTC – 10 hours
WDT Western Daylight Time Australia UTC + 9 hours
WEDT Western European Daylight Time Europe UTC + 1 hour
WEST Western European Summer Time Europe UTC + 1 hour
WET Western European Time Europe UTC
WST Western Summer Time Australia UTC + 9 hours
WST Western Standard Time Australia UTC + 8 hours
X X-ray Time Zone Military UTC – 11 hours
Y Yankee Time Zone Military UTC – 12 hours
Z Zulu Time Zone Military UTC

The decrease in daylight during the winter months is due to Earth’s axial tilt of 23 degrees. If the Earth was not tilted on it’s axis, the length of day and night would remain steady year long. During winter in the northern hemisphere there is less daylight hours, and the southern hemisphere in turn has longer daylight hours and experiences summer.

The main purpose of Daylight Saving Time (called “Summer Time” in many places in the world) is to make better use of daylight. In Ireland we advance our clocks forward by one hour in Spring to maximise daylight for the summer months. This has the effect of moving an hour of daylight from the morning to the evening. In Winter the clocks are then changed back by one hour to maximise daylight during morning hours.