How many hours is PST behind AST?
As abbreviations, AST is always 4 hours ahead of PST: PST is UTC−8 and AST is UTC−4. To convert, add 4 hours.
Check which label you actually need: PST (Pacific Time is on PDT today). A time written with an abbreviation that is not in use is usually meant as the local time, so convert between the places instead: right now AST is 3 hours ahead of PST.
When the PST to AST time difference changes
For most of the year AST is 3 hours ahead of PST. From 1 November to 31 December 2026, AST is 4 hours ahead of PST instead, because the two places change their clocks on different dates. Meetings booked by the usual gap land an hour off in those weeks.
| Dates | AST vs PST | Length |
|---|---|---|
| 8 March 2026 to 31 October 2026 | 3 hours ahead | 238 days |
| 1 November 2026 to 31 December 2026 | 4 hours ahead | 61 days |
| 1 January 2027 to 13 March 2027 | 4 hours ahead | 72 days |
| 14 March 2027 to 6 November 2027 | 3 hours ahead | 238 days |
| 7 November 2027 to 31 December 2027 | 4 hours ahead | 55 days |
When PST and AST are both at work
- When AST is 3 hours ahead of PST: 5 shared office hours, 09:00 to 14:00 in PST (12:00 to 17:00 in AST).
- When AST is 4 hours ahead of PST: 4 shared office hours, 09:00 to 13:00 in PST (13:00 to 17:00 in AST).