AST: which one do you mean?
AST means 2 different things, and they are hours apart. If you received a timestamp labelled AST, the sender's location decides which of these applies, so pick it below.
Atlantic Standard Time · North America
16:36:35
Sunday, 15 November 2026
- abbreviation denotes
- -04:00
- in force right now
- AST (UTC-04:00)
- use in code
- America/Halifax
- also valid
- America/Puerto_Rico
- next clock change
- 14 Mar 2027 03:00 → ADT
Arabia Standard Time · Asia
23:36:35
Sunday, 15 November 2026
- abbreviation denotes
- +03:00
- in force right now
- UTC+03:00 (UTC+03:00)
- use in code
- Asia/Riyadh
- also valid
- Asia/Baghdad, Asia/Qatar
- next clock change
- none, fixed offset
Right now this zone is on UTC+03:00, not AST. They are the same place at different times of year.
Use the IANA name, not the abbreviation
Python
from datetime import datetime
from zoneinfo import ZoneInfo
# right: an IANA zone carries the full history of rule changes
now = datetime.now(ZoneInfo("America/Halifax"))
print(now.isoformat(), now.tzname())
# wrong: an abbreviation is not resolvable, and a hard-coded offset
# silently rots the next time the rules change
# now = datetime.now(timezone(timedelta(hours=...))) # don'tAST questions
What does AST stand for?
AST has 2 distinct meanings in active use: Atlantic Standard Time (-04:00, America/Halifax); Arabia Standard Time (+03:00, Asia/Riyadh). Which one applies depends entirely on who wrote the timestamp.
What time is it in AST right now?
Atlantic Standard Time: 16:36 on Sunday (AST); Arabia Standard Time: 23:36 on Sunday (UTC+03:00).
Which IANA timezone should I use instead of AST?
America/Halifax for Atlantic Standard Time, Asia/Riyadh for Arabia Standard Time. Date libraries cannot resolve bare abbreviations, and an abbreviation carries no daylight-saving history, so a stored offset silently rots when a government changes the rules.