EST vs EDT, GMT vs UTC: time zone abbreviations explained
EST is not the same as EDT, and GMT is not quite UTC. What common time zone abbreviations mean, when daylight saving changes them, and how to avoid missed calls.
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Tools for this job: Time Zone Meeting Planner · Timestamp Converter
A meeting invite says 10:00 EST in July. Technically, Eastern Standard Time is not in use in July; New York is on Eastern Daylight Time. Most people mean “New York time” either way, but the mix-up causes hour-off errors whenever someone converts the abbreviation literally.
Common abbreviations
| Abbreviation | Offset | Used |
|---|---|---|
| EST / EDT | UTC−5 / UTC−4 | US East, winter / summer |
| CST / CDT | UTC−6 / UTC−5 | US Central |
| PST / PDT | UTC−8 / UTC−7 | US West |
| GMT / BST | UTC+0 / UTC+1 | UK, winter / summer |
| CET / CEST | UTC+1 / UTC+2 | Most of Europe |
| IST | UTC+5:30 | India (all year) |
| NPT | UTC+5:45 | Nepal (all year) |
Abbreviations are not unique. IST also means Irish Standard Time and Israel Standard Time, and CST is China Standard Time as well as US Central. That is another reason to name a city instead.
GMT versus UTC
UTC, Coordinated Universal Time, is the world's reference time, kept by atomic clocks. GMT is historically the time at Greenwich and today is the UK's winter time zone. For everyday scheduling they are the same clock. The difference is that UTC is a standard and never changes for summer, while “GMT” as UK time switches to BST in summer. Computers and servers use UTC.
Daylight saving dates in 2026
- United States and Canada (most areas): from 8 March to 1 November.
- UK and EU: from 29 March to 25 October.
- India, Nepal, China, Japan and most of Africa and South America: no daylight saving.
For two to three weeks each spring and one week each autumn, the US and Europe are out of step, and the usual gap between New York and London shrinks from five hours to four. Recurring meetings drift by an hour for one side during those weeks.
How to avoid mistakes
- Name a city: “10:00 New York time” is unambiguous all year.
- Use “ET” or “PT” to mean whatever is in force, rather than EST or PST.
- Send calendar invites, which store the event in UTC and show each person their local time.
- Check across a change date with the Time Zone Meeting Planner, which compares cities hour by hour using current daylight-saving rules.
Places with unusual offsets
Not every zone is a whole number of hours from UTC. India is UTC+5:30, Nepal UTC+5:45, parts of Australia UTC+9:30 or +10:30 in summer, and Newfoundland UTC−3:30. Scheduling tools that only offer whole hours get these wrong, so check the minutes when anyone in a meeting is in one of these places.
Offsets in timestamps
Machine-readable times carry the offset explicitly, such as 2026-10-03T10:00:00-04:00, or use UTC with a Z: 2026-10-03T14:00:00Z. Both are the same moment. The Timestamp Converter shows any time in UTC and your own zone. For planning calls across several zones, see scheduling a meeting across time zones.