UTC to AST Time Converter
AST is 3 hours behind UTC. UTC is the zero point, UTC±00:00, and Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00).
Best Time to Call Between UTC and AST
Both zones are inside normal business hours between 12:00 PM and 5:00 PM UTC — that's 9:00 AM to 2:00 PM AST. That's a 5-hour window.
both at work UTC only AST only neither — hours along the strip are UTC.
Common Times Converted
UTC on the left, AST on the right.
UTC to AST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| UTC | AST | Working hours |
|---|---|---|
| 12:00 AM | 9:00 PM prev day | — |
| 1:00 AM | 10:00 PM prev day | — |
| 2:00 AM | 11:00 PM prev day | — |
| 3:00 AM | 12:00 AM | — |
| 4:00 AM | 1:00 AM | — |
| 5:00 AM | 2:00 AM | — |
| 6:00 AM | 3:00 AM | — |
| 7:00 AM | 4:00 AM | — |
| 8:00 AM | 5:00 AM | — |
| 9:00 AM | 6:00 AM | UTC only |
| 10:00 AM | 7:00 AM | UTC only |
| 11:00 AM | 8:00 AM | UTC only |
| 12:00 PM | 9:00 AM | Both zones |
| 1:00 PM | 10:00 AM | Both zones |
| 2:00 PM | 11:00 AM | Both zones |
| 3:00 PM | 12:00 PM | Both zones |
| 4:00 PM | 1:00 PM | Both zones |
| 5:00 PM | 2:00 PM | AST only |
| 6:00 PM | 3:00 PM | AST only |
| 7:00 PM | 4:00 PM | AST only |
| 8:00 PM | 5:00 PM | — |
| 9:00 PM | 6:00 PM | — |
| 10:00 PM | 7:00 PM | — |
| 11:00 PM | 8:00 PM | — |
What UTC and AST Actually Are
UTC — Coordinated Universal Time
The global reference standard. Aviation, computing and science run on it. Standing at UTC as written, and the region does not change its clocks, so that offset holds all year.
UTC is not a place. It is a computed standard, kept within a second of mean solar time at Greenwich by atomic clocks, and it is the reference every other zone is defined against.
AST — Atlantic Standard Time
Halifax, San Juan, Santo Domingo, Bermuda. Standing at UTC-4:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to AST. AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Atlantic Standard Time is the only North American zone whose name is more commonly associated, worldwide, with a completely different zone — Arabia Standard Time.
What This Means in Practice
This gap is not fixed
AST changes its clocks and UTC does not, so the difference between them moves by an hour twice a year. A recurring meeting set now will drift for one side from Sunday, November 1, 2026 unless someone resets it.
Major Cities in Each Zone
Cities on AST
Frequently Asked Questions
What is the time difference between UTC and AST?
AST is 3 hours behind UTC. That is the live figure. Taken strictly as written, the gap between UTC and AST is 4 hours — the two differ because at least one of these regions is currently on daylight saving.
What is 9:00 AM UTC in AST?
9:00 AM UTC is 6:00 AM AST.
What are the best hours to schedule a call between UTC and AST?
Between 12:00 PM and 5:00 PM UTC, which is 9:00 AM to 2:00 PM AST. Both sides are inside normal business hours through that window.
Does the difference between UTC and AST change during the year?
Yes. AST observes daylight saving and UTC does not, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, November 1, 2026.
Does AST always mean Atlantic Standard Time?
AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.