EST vs EDT, GMT vs BST: Time Zone Abbreviations and DST Dates for 2026–2027
Time-zone abbreviations cause more missed meetings than anything else in scheduling. The two most common mix-ups: "EST" is only correct in winter, and "GMT" is not the time in London for half the year. Here is what each abbreviation means, and when the clocks change.
What the abbreviations mean
| Region | Winter | Summer | Example cities |
|---|---|---|---|
| US Eastern | EST, UTC−5 | EDT, UTC−4 | New York, Toronto, Miami |
| US Central | CST, UTC−6 | CDT, UTC−5 | Chicago, Dallas |
| US Mountain | MST, UTC−7 | MDT, UTC−6 (not Arizona) | Denver, Phoenix (MST all year) |
| US Pacific | PST, UTC−8 | PDT, UTC−7 | Los Angeles, Seattle |
| UK & Ireland | GMT, UTC+0 | BST/IST, UTC+1 | London, Dublin |
| Central Europe | CET, UTC+1 | CEST, UTC+2 | Paris, Berlin, Madrid |
| India | IST, UTC+5:30 all year | Delhi, Mumbai, Bengaluru | |
| Gulf | GST, UTC+4 all year | Dubai, Abu Dhabi | |
| Western Indonesia | WIB, UTC+7 all year | Jakarta, Surabaya, Medan (Bali is on WITA, UTC+8). See WIB to EST | |
| Singapore | SGT, UTC+8 all year | Singapore, Kuala Lumpur | |
| Japan | JST, UTC+9 all year | Tokyo, Osaka | |
| Sydney | AEDT, UTC+11 (Oct–Apr) | AEST, UTC+10 (Apr–Oct) | Sydney, Melbourne (Brisbane AEST all year) |
To avoid the mix-up, say "Eastern Time" or "ET" rather than EST. Or name a city ("3 PM New York time"), which is always correct.
Clock-change dates 2026–2027
Computed from the IANA time-zone database:
| Region | Clocks go back | Clocks go forward | Then back again |
|---|---|---|---|
| United States & Canada | Sun 1 Nov 2026, 2:00 → 1:00 | Sun 14 Mar 2027, 2:00 → 3:00 | Sun 7 Nov 2027 |
| UK, Ireland, Portugal | Sun 25 Oct 2026, 2:00 → 1:00 | Sun 28 Mar 2027, 1:00 → 2:00 | Sun 31 Oct 2027 |
| EU (CET/CEST) | Sun 25 Oct 2026, 3:00 → 2:00 | Sun 28 Mar 2027, 2:00 → 3:00 | Sun 31 Oct 2027 |
| Sydney / Melbourne | Sun 4 Apr 2027, 3:00 → 2:00 | Sun 3 Oct 2027, 2:00 → 3:00 | Sun 2 Apr 2028 |
India, Indonesia, the UAE, Singapore, Japan, Arizona and Queensland don't change their clocks.
When the gaps shift
Because regions switch on different dates, the gap between two cities can change several times a year:
- New York ↔ London is usually 5 hours, but only 4 hours between 25 October and 1 November 2026, and again between 14 and 28 March 2027. See EST to BST.
- New York ↔ India is 9 h 30 min in US summer and 10 h 30 min in US winter (from 1 November 2026 to 14 March 2027). See EST to IST.
- London ↔ Sydney moves between 9, 10 and 11 hours over the year, because the two hemispheres change their clocks in opposite directions. See BST to AEST.
Every time-zone pair page lists these periods for the next 12 months, with a 24-hour conversion table and the best meeting window.
Scheduling tips
- Write times as a city or UTC offset ("15:00 UTC", "9 AM Chicago"), not as an ambiguous abbreviation.
- Calendar invites store times in UTC, so they adjust automatically — a time typed into the body of an email doesn't.
- Recurring meetings across regions shift by an hour during the "shoulder weeks" in March/April and October/November. Warn attendees.
- Use the timezone converter to find a slot inside everyone's working hours.