UTC Offsets and Time Zone Abbreviations

This page is the reference: what an abbreviation means, and what a given offset reads as elsewhere. To convert a specific time from one place to another, including the day change when it crosses midnight, use convert a time between two zones.

One warning about abbreviations, since this is the page that lists them. They are not unique. CST is Central Standard Time in North America, China Standard Time and Cuba Standard Time, and IST covers India, Ireland and Israel. Anything that has to be unambiguous should carry a UTC offset or a full zone name, never three letters.

Time zones are defined as offsets from UTC (Coordinated Universal Time).

Major time zones:

Note: Daylight saving time (DST) shifts most zones by +1 hour. Everything in this table, and everything the converter above prints, is standard time with no DST applied.

Two abbreviations in that table clash, and it is worth knowing about. CST means Central Standard Time at UTC-6 in North America and China Standard Time at UTC+8 in Asia, a fourteen-hour gap between two identical letters. IST is India Standard Time at UTC+5:30, Irish Standard Time at UTC+1, and Israel Standard Time at UTC+2. Abbreviations are not unique and never have been, which is why calendar software works in named zones like America/Chicago rather than letters. When you are scheduling across borders, write the UTC offset.

Fixed offsets are the honest way to show how zones line up, but they can’t capture the part that actually trips up scheduling: daylight saving time. Many regions shift by an hour for part of the year, and crucially they don’t all switch on the same date, so the gap between two cities can change several times across the year. Before booking a cross-border call, confirm whether either side is currently on summer time.

Two quirks are worth remembering. Offsets aren’t all whole hours, as the India row above shows at UTC+5:30, and Nepal goes further to UTC+5:45. And the International Date Line means some neighbors sit nearly a full day apart, so you can cross a short stretch of ocean and land on a different calendar date. An offset explains the clock, but not always the date.