Highlighted rows fall within 09:00–18:00 in both places: 6 shared working hours.
How many hours is GMT ahead of ADT?
As abbreviations, ADT is always 3 hours behind of GMT: GMT is UTC+0 and ADT is UTC−3. To convert, subtract 3 hours.
When the GMT to ADT time difference changes
For most of the year ADT is 3 hours behind of GMT. From 1 November to 31 December 2026, ADT is 4 hours behind of GMT 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
ADT vs GMT
Length
8 March 2026 to 31 October 2026
3 hours behind
238 days
1 November 2026 to 31 December 2026
4 hours behind
61 days
1 January 2027 to 13 March 2027
4 hours behind
72 days
14 March 2027 to 6 November 2027
3 hours behind
238 days
7 November 2027 to 31 December 2027
4 hours behind
55 days
Calling hours for GMT and ADT
When ADT is 3 hours behind of GMT: 5 shared office hours, 12:00 to 17:00 in GMT (09:00 to 14:00 in ADT).
When ADT is 4 hours behind of GMT: 4 shared office hours, 13:00 to 17:00 in GMT (09:00 to 13:00 in ADT).
Frequently asked questions about GMT and ADT time
How many hours ahead is ADT of GMT?
ADT (UTC−3) is 3 hours behind of GMT (UTC+0).
Does the time difference between GMT and ADT change?
Yes. It is usually 3 hours behind, but changes when one side moves its clocks: 4 hours behind from 1 November to 31 December 2026; 4 hours behind from 1 January to 13 March 2027.