timezone_abbreviations_list()

Introduction

A timezone abbreviation is a short 2-5 letter code such as EST, GMT, or CEST that names a region's offset from Coordinated Universal Time (UTC). PHP can list every abbreviation it knows about, along with the IANA timezone identifiers (like America/New_York) each one maps to.

This chapter explains how to retrieve that list, why abbreviations are unreliable on their own, and gives a reference table of common codes.

Why abbreviations are ambiguous

Unlike IANA identifiers, abbreviations are not unique. CST alone can mean Central Standard Time (North America, UTC-6), China Standard Time (UTC+8), or Cuba Standard Time. BST is British Summer Time or Bangladesh Standard Time. Because the same code maps to several regions, you should never store or configure a timezone by its abbreviation. Always resolve to an IANA identifier (for example Europe/London) and feed that to date_default_timezone_set() or a DateTimeZone object.

This is exactly what the abbreviations list is for: turning a code you received (say, from user input) into the candidate identifiers it could represent — see timezone_name_from_abbr() for picking a single match.

Listing every abbreviation

Both functions return an associative array. Each key is a lowercase abbreviation; each value is an array of zones, where every zone has three fields:

• dst — true if the entry is a daylight-saving variant.
• offset — the UTC offset in seconds.
• timezone_id — the IANA identifier (may be null for offsets with no named zone).

<?php
// PHP 8.2+ (use timezone_abbreviations_list() on older versions)
$abbreviations = DateTimeZone::listAbbreviations();

print_r($abbreviations['acst']);

Output:

Array
(
    [0] => Array
        (
            [dst] =>
            [offset] => 34200
            [timezone_id] => Australia/Adelaide
        )
    ...
)

The offset 34200 seconds is 34200 / 3600 = 9.5 hours, i.e. UTC+9:30.

Mapping abbreviations to identifiers and offsets

To turn the raw structure into readable rows, iterate the outer array and then each zone:

<?php
$abbreviations = DateTimeZone::listAbbreviations();

foreach ($abbreviations as $abbr => $zones) {
    foreach ($zones as $zone) {
        $hours = $zone['offset'] / 3600;
        printf(
            "%-5s => %-25s (UTC %+.1f)\n",
            strtoupper($abbr),
            $zone['timezone_id'] ?? '(unnamed)',
            $hours
        );
    }
}

A few sample lines of the output:

GMT   => Europe/London             (UTC +0.0)
GMT   => Africa/Abidjan            (UTC +0.0)
CET   => Europe/Paris              (UTC +1.0)

The list is large (thousands of rows), so in practice you filter it to the codes you care about rather than printing all of it.

Common timezone abbreviations

Below is a reference list of common timezone abbreviations (the array keys are lowercase in PHP; shown uppercase here for readability):

• ACDT - Australian Central Daylight Time
• ACST - Australian Central Standard Time
• ACT - Acre Time
• ADT - Atlantic Daylight Time
• AEDT - Australian Eastern Daylight Time
• AEST - Australian Eastern Standard Time
• AFT - Afghanistan Time
• AKDT - Alaska Daylight Time
• AKST - Alaska Standard Time
• AMST - Amazon Summer Time
• AMT - Amazon Time
• ART - Argentina Time
• AST - Atlantic Standard Time
• AWST - Australian Western Standard Time
• AZOST - Azores Standard Time
• AZT - Azerbaijan Time
• BDT - Brunei Time
• BNT - Brunei Darussalam Time
• BOT - Bolivia Time
• BRST - Brasilia Summer Time
• BRT - Brasilia Time
• BST - British Summer Time
• BTT - Bhutan Time
• CAT - Central Africa Time
• CCT - Cocos Islands Time
• CDT - Central Daylight Time
• CEST - Central European Summer Time
• CET - Central European Time
• CHADT - Chatham Island Daylight Time
• CHAST - Chatham Island Standard Time
• CHOT - Choibalsan Standard Time
• CHST - Chamorro Standard Time
• CHT - Chuuk Time
• CKT - Cook Island Time
• CLST - Chile Summer Time
• CLT - Chile Standard Time
• COT - Colombia Time
• CST - Central Standard Time
• CT - Central Time
• CVT - Cape Verde Time
• CWST - Central Western Standard Time
• CXT - Christmas Island Time
• DAVT - Davis Time
• DDUT - Dumont-d'Urville Time
• EASST - Easter Island Summer Time
• EAST - Easter Island Standard Time
• EAT - Eastern Africa Time
• ECT - Eastern Caribbean Time
• EDT - Eastern Daylight Time
• EEST - Eastern European Summer Time
• EET - Eastern European Time
• EGST - Eastern Greenland Summer Time
• EGT - Eastern Greenland Time
• EIT - Eastern Indonesian Time
• EST - Eastern Standard Time
• FET - Further Eastern European Time
• FJT - Fiji Time
• FKST - Falkland Islands Summer Time
• FKT - Falkland Islands Time
• FNT - Fernando de Noronha Time
• GALT - Galapagos Time
• GAMT - Gambier Islands Time
• GET - Georgia Standard Time
• GFT - French Guiana Time
• GILT - Gilbert Island Time
• GIT - Gambier Island Time
• GMT - Greenwich Mean Time
• GST - Gulf Standard Time
• GYT - Guyana Time
• HADT - Hawaii-Aleutian Daylight Time
• HAST - Hawaii-Aleutian Standard Time
• HKT - Hong Kong Time
• HST - Hawaii Standard Time
• ICT - Indochina Time
• IDT - Israel Daylight Time
• IRDT - Iran Daylight Time
• IRST - Iran Standard Time
• IST - India / Irish / Israel Standard Time (ambiguous)
• JST - Japan Standard Time
• KST - Korea Standard Time
• MDT - Mountain Daylight Time
• MSK - Moscow Standard Time
• MST - Mountain Standard Time
• NZDT - New Zealand Daylight Time
• NZST - New Zealand Standard Time
• PDT - Pacific Daylight Time
• PHT - Philippine Time
• PKT - Pakistan Standard Time
• PST - Pacific Standard Time
• SGT - Singapore Time
• UTC - Coordinated Universal Time
• WAT - West Africa Time
• WEST - Western European Summer Time
• WET - Western European Time
• WIB - Western Indonesian Time
• WITA - Central Indonesian Time

The list above is a common subset. DateTimeZone::listAbbreviations() returns the complete array of every registered abbreviation, which you should iterate programmatically (as shown above) rather than relying on a hand-maintained list.

Related functions

• PHP Timezones — overview of DateTimeZone and IANA identifiers.
• timezone_identifiers_list() — list every IANA identifier PHP supports.
• timezone_name_from_abbr() — resolve a single abbreviation to one identifier.
• date_default_timezone_set() — set the script-wide default timezone.

Practice