Standard vs daylight
In North America and Europe the winter (standard) and summer (daylight) names differ. S is Standard, D is Daylight.
| Code | Meaning | Offset |
|---|---|---|
| EST / EDT | US Eastern standard / daylight | UTC−5 / UTC−4 |
| PST / PDT | US Pacific standard / daylight | UTC−8 / UTC−7 |
| GMT / BST | Greenwich Mean Time / British Summer Time | UTC+0 / UTC+1 |
| CET / CEST | Central European / summer | UTC+1 / UTC+2 |
| KST / JST | Korea / Japan Standard Time | UTC+9 |
“3pm EST” in July literally means 3pm at UTC−5, which is 4pm in New York. The sender almost certainly meant 3pm New York time; when in doubt, ask.
Same letters, different places
| Code | Possible meanings |
|---|---|
| IST | India UTC+5:30 / Ireland UTC+1 / Israel UTC+2 |
| CST | US Central UTC−6 / China UTC+8 |
| BST | British Summer Time UTC+1 / Bougainville UTC+11 |
A supplier in China writing “CST” usually means China time; mix that with a US schedule and you are 14 hours apart.
How to write it safely
- Use the city, not the code: “3pm New York time” is right in every season.
- Add the offset: “15:00 New York (UTC−4)”.
- List the other side too: “15:00 New York / 20:00 London, 1 Oct”.
- Send a calendar invite: each calendar shows it in its owner’s zone.
Codes in the app
Code, offset and DST per city
Each city card on the World Time Board Board tab shows the code and offset in use that day. In September New York shows EDT · UTC-4 · DST and London BST · UTC+1 · DST. Turn it on or off with Show zone code & DST in Settings.
Convert the time you were sent
If an email says “3pm New York”, set New York as the From city on the Convert tab, pick the date and 15:00, and read every other city at once.
FAQ
What about ET or PT without S or D?
They are used to mean “whatever Eastern/Pacific time is in effect”, so they are safer than EST/EDT.
Some cities show GMT+3 instead of a code.
Where the time zone data has no widely used abbreviation, the offset is shown instead.
World Time Board - Time Zones
No sign-in, no internet needed, and your city list stays on your phone. Free on Android.