ZipKit
Cheatsheet

Time Zone List Cheatsheet

Code should identify a time zone by its IANA name, such as America/New_York, and never by an abbreviation like CST or a fixed offset. This sheet lists the standard and summer offsets of 40 widely used zones, the 2026 clock-change dates, and the lookups that work in JavaScript, Python, PHP and the shell. It clears up one confusion: an offset such as UTC-05:00 is one moment's value, while a zone name carries the whole rule history. The sheet assumes you know what UTC is.

Quick reference

Common zones and offsets for 2026

Offsets come from tz database release 2026b, read on 2026-01-15 (winter in the north) and 2026-07-15 (summer in the north). Where the two columns match, the zone has no clock change in 2026.

IANA name January offset July offset Notes
`UTC` +00:00 +00:00 Never changes
`America/New_York` -05:00 EST -04:00 EDT US rules
`America/Chicago` -06:00 CST -05:00 CDT US rules
`America/Denver` -07:00 MST -06:00 MDT US rules
`America/Phoenix` -07:00 MST -07:00 MST No daylight saving
`America/Los_Angeles` -08:00 PST -07:00 PDT US rules
`America/Anchorage` -09:00 AKST -08:00 AKDT US rules
`Pacific/Honolulu` -10:00 HST -10:00 HST No daylight saving
`America/Mexico_City` -06:00 CST -06:00 CST No daylight saving
`America/Sao_Paulo` -03:00 -03:00 No daylight saving
`America/Argentina/Buenos_Aires` -03:00 -03:00 No daylight saving
`Europe/London` +00:00 GMT +01:00 BST EU dates
`Europe/Dublin` +00:00 GMT +01:00 IST EU dates
`Europe/Paris` +01:00 CET +02:00 CEST EU dates
`Europe/Berlin` +01:00 CET +02:00 CEST EU dates
`Europe/Athens` +02:00 EET +03:00 EEST EU dates
`Europe/Kyiv` +02:00 EET +03:00 EEST EU dates, renamed from `Europe/Kiev`
`Europe/Istanbul` +03:00 +03:00 Permanent +03
`Europe/Moscow` +03:00 MSK +03:00 MSK No daylight saving
`Africa/Cairo` +02:00 EET +03:00 EEST Own dates, see below
`Africa/Lagos` +01:00 WAT +01:00 WAT No daylight saving
`Africa/Johannesburg` +02:00 SAST +02:00 SAST No daylight saving
`Africa/Nairobi` +03:00 EAT +03:00 EAT No daylight saving
`Asia/Dubai` +04:00 +04:00 No daylight saving
`Asia/Tehran` +03:30 +03:30 Half-hour offset
`Asia/Karachi` +05:00 PKT +05:00 PKT No daylight saving
`Asia/Kolkata` +05:30 IST +05:30 IST Half-hour offset
`Asia/Kathmandu` +05:45 +05:45 45-minute offset
`Asia/Dhaka` +06:00 +06:00 No daylight saving
`Asia/Bangkok` +07:00 +07:00 No daylight saving
`Asia/Jakarta` +07:00 WIB +07:00 WIB No daylight saving
`Asia/Shanghai` +08:00 CST +08:00 CST One zone for all of China
`Asia/Singapore` +08:00 +08:00 No daylight saving
`Asia/Tokyo` +09:00 JST +09:00 JST No daylight saving
`Asia/Seoul` +09:00 KST +09:00 KST No daylight saving
`Australia/Perth` +08:00 AWST +08:00 AWST No daylight saving
`Australia/Adelaide` +10:30 ACDT +09:30 ACST Southern summer in January
`Australia/Sydney` +11:00 AEDT +10:00 AEST Southern summer in January
`Pacific/Auckland` +13:00 NZDT +12:00 NZST Southern summer in January
`Pacific/Chatham` +13:45 +12:45 45-minute offset

Zones with only a numeric label, such as +03, have no widely used English abbreviation, so the database uses the offset itself.

2026 clock changes

Region Spring forward Fall back Rule
United States Sun 2026-03-08, 02:00 local Sun 2026-11-01, 02:00 local Second Sunday of March, first Sunday of November
European Union and UK Sun 2026-03-29, 01:00 UTC Sun 2026-10-25, 01:00 UTC Last Sunday of March and October
Egypt (`Africa/Cairo`) Fri 2026-04-24, 00:00 local Fri 2026-10-30, 00:00 local Last Friday of April and October
Australia (Sydney, Adelaide) Sun 2026-10-04, 02:00 standard time Sun 2026-04-05, 03:00 summer time First Sunday of October and April
New Zealand (`Pacific/Auckland`) Sun 2026-09-27, 02:00 standard time Sun 2026-04-05, 03:00 summer time Last Sunday of September, first Sunday of April

All EU countries switch at the same instant, so a Berlin clock and an Athens clock change within the same hour of UTC.

Name format rules

Rule Example
Form is `Area/Location` `Pacific/Honolulu`
Areas are continents or oceans `Africa`, `America`, `Antarctica`, `Asia`, `Atlantic`, `Australia`, `Europe`, `Indian`, `Pacific`
North and South America share one area `America/Sao_Paulo`
Extra level for disambiguation `America/Indiana/Petersburg`
ASCII letters, `.`, `-` and `_` only, no digits in new names `America/Port-au-Prince`
Each part is at most 14 characters `America/Noronha`, not `America/Fernando_de_Noronha`
Names are case-sensitive in the reference implementation `Europe/Paris`, not `europe/paris`

Etc zones have inverted signs

Name Actual offset
`Etc/GMT+5` UTC-05:00
`Etc/GMT-14` UTC+14:00
`Etc/UTC` UTC+00:00

The sign follows the POSIX convention, where positive means west of Greenwich. Only whole hours from Etc/GMT-14 to Etc/GMT+12 exist.

Common patterns

Show one instant in many zones

const d = new Date("2026-10-05T12:00:00Z");
for (const z of ["UTC", "America/New_York", "Europe/Berlin", "Asia/Kolkata", "Asia/Tokyo", "Australia/Sydney"]) {
  console.log(z.padEnd(18), d.toLocaleString("sv-SE", { timeZone: z }));
}
UTC                2026-10-05 12:00:00
America/New_York   2026-10-05 08:00:00
Europe/Berlin      2026-10-05 14:00:00
Asia/Kolkata       2026-10-05 17:30:00
Asia/Tokyo         2026-10-05 21:00:00
Australia/Sydney   2026-10-05 23:00:00

The sv-SE locale prints YYYY-MM-DD HH:mm:ss, which sorts and reads well in logs. Pass timeZone and the Date itself is never changed. The JS Intl.DateTimeFormat Playground shows the same options interactively.

Convert a stored UTC time to the user's zone

from datetime import datetime, timezone
from zoneinfo import ZoneInfo

stored_utc = datetime(2026, 10, 5, 12, tzinfo=timezone.utc)
stored_zone = "Asia/Kolkata"
print(stored_utc.astimezone(ZoneInfo(stored_zone)).isoformat())
2026-10-05T17:30:00+05:30

Store the instant in UTC and, separately, the zone name the user picked. Convert only when you display. Storing just +05:30 loses the rules, so a later date in a daylight saving zone would come out wrong.

Handle the spring gap and the fall repeat

from datetime import datetime, timezone
from zoneinfo import ZoneInfo

ny = ZoneInfo("America/New_York")
print(datetime(2026, 3, 8, 2, 30, tzinfo=ny).astimezone(timezone.utc).isoformat())
print(datetime(2026, 11, 1, 1, 30, tzinfo=ny).astimezone(timezone.utc).isoformat())
print(datetime(2026, 11, 1, 1, 30, fold=1, tzinfo=ny).astimezone(timezone.utc).isoformat())
2026-03-08T07:30:00+00:00
2026-11-01T05:30:00+00:00
2026-11-01T06:30:00+00:00

At 02:00 on 2026-03-08 New York jumps to 03:00, so 02:30 never happens and Python silently maps it to 03:30 EDT. At 02:00 on 2026-11-01 the clock returns to 01:00, so 01:30 happens twice and fold picks the first (0) or second (1) one. Ask users for a zone and an exact offset, or schedule in UTC, when the hour matters.

List and validate zone names

const names = Intl.supportedValuesOf("timeZone");
console.log(names.length, names.slice(0, 3));
try {
  new Date().toLocaleString("en-US", { timeZone: "America/Nowhere" });
} catch (e) {
  console.log(e.name + ": " + e.message);
}
418 [ 'Africa/Abidjan', 'Africa/Accra', 'Africa/Addis_Ababa' ]
RangeError: Invalid time zone specified: America/Nowhere

The count depends on the runtime (this run used Node.js 22). Python's zoneinfo.available_timezones() returned 498 on the test machine (the count depends on the installed tzdata) and PHP's DateTimeZone::listIdentifiers() returned 419, because each includes a different set of legacy aliases. Validate user input against the list of the runtime that will parse it.

Read the system zone and set it for one command

TZ=Asia/Tokyo date -d @1791201600 '+%F %T %Z %z'
date -u -d 'TZ="America/New_York" 2026-10-05 08:00' +%FT%TZ
2026-10-05 21:00:00 JST +0900
2026-10-05T12:00:00Z

The TZ environment variable overrides the zone for a single command, and GNU date accepts an inline TZ="..." prefix in the date string. In JavaScript, Intl.DateTimeFormat().resolvedOptions().timeZone returns the zone of the current runtime.

Pitfalls

  • Abbreviations are ambiguous: CST means US Central Standard Time and China Standard Time, and IST means India, Ireland or Israel. The tz database documentation says to use numeric offsets such as -0600 instead of abbreviations when a program must be unambiguous. Never parse an abbreviation to find a zone.
  • The abbreviation depends on the locale: Europe/Berlin formats as GMT+2 with en-US and as MESZ with de-DE in Node.js, because en-US has no short name for Central European Summer Time. Do not compare or store the formatted label.
  • Etc/GMT signs look backward: Etc/GMT+5 is five hours behind UTC, so 2026-10-05T12:00:00Z shows as 2026-10-05T07:00:00-05:00 in Python there. Developers who read +5 as east of Greenwich are off by ten hours. Prefer a real Area/Location name for people and use Etc/GMT names only for fixed machine offsets.
  • Not every day has 24 hours: On 2026-03-08 New York has 23 hours and on 2026-11-01 it has 25, while 2026-10-05 has 24. A daily job, a "midnight to midnight" report or a 24-hour timer drifts across those days unless you work in UTC or calendar dates.
  • Hard-coded DST dates go stale: governments change rules, and the tz database keeps shipping releases for it. Release 2026b (2026-04-22) put British Columbia on permanent -07, release 2026c (2026-07-08) did the same for Alberta and set Morocco to permanent +00 from 2026-09-20, release 2026d (2026-09-11) covered the Northwest Territories, and release 2026e (2026-09-29) covered Manitoba. A runtime with older zone data, such as Node.js 22 here with data from 2025b, still gives the old answers. Keep the OS or tzdata package updated.
  • Renamed zones keep old names as links: Europe/Kiev became Europe/Kyiv and Asia/Rangoon became Asia/Yangon. The old names still resolve in most runtimes, but a dropdown built from one runtime may not match a database built from another.
  • Offsets are not zones: the same -05:00 appears in America/New_York in winter and America/Chicago in summer. Saving only the offset makes it impossible to compute a future local time correctly.
  • Python needs zone data on some systems: Windows has no IANA database, so ZoneInfo("America/New_York") raises ZoneInfoNotFoundError unless the tzdata package from PyPI is installed. Declare it as a dependency when you ship cross-platform.

Related ZipKit tools

  • JS Intl.DateTimeFormat Playground — try timeZone and timeZoneName options and see the formatted result for any zone
  • Unix Timestamp Converter — turn the instant you store into a readable date and back

Related cheatsheets