ADT to GMT Time Converter

Convert Atlantic Daylight Time (ADT) to Greenwich Mean Time (GMT). Both time zones are shown live below; current offset between them is 4 hours ahead.

Halifax · Atlantic Daylight Time
21:29:47
Tuesday, May 12, 2026
ADT · UTC-03:00
London · Greenwich Mean Time
01:29:47
Wednesday, May 13, 2026
GMT+1 · UTC+01:00

Convert a specific time

From: ADT (Halifax)
To: GMT (London)
--:--

Daylight Saving status right now

ADT (Atlantic Daylight Time)
Observes DST
Yes
In DST right now
Yes
Next fall back
2026-11-01
Offset shift
UTC-03:00 → UTC-04:00
GMT (Greenwich Mean Time)
Observes DST
Yes
In DST right now
Yes
Next fall back
2026-10-25
Offset shift
UTC+01:00 → UTC+00:00

When can ADT and GMT meet?

00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
ADT
GMT
Both zones in working hours (9am-5pm)
One zone working
Off-hours
Columns are hours of the day in Halifax (ADT). Each row shows the local working-hours state in that zone for the same moment in time.
4 hours of overlap during standard 9am-5pm working hours.
Best meeting window: 09:00–12:00 ADT (13:00–16:00 GMT).

Hour-by-hour ADT to GMT conversion table

ADT time (Halifax)GMT time (London)Status
00:00 Tue04:00 TueOff-hours both sides
01:00 Tue05:00 TueOff-hours both sides
02:00 Tue06:00 TueOff-hours both sides
03:00 Tue07:00 TueOff-hours both sides
04:00 Tue08:00 TueOff-hours both sides
05:00 Tue09:00 TueGMT working
06:00 Tue10:00 TueGMT working
07:00 Tue11:00 TueGMT working
08:00 Tue12:00 TueGMT working
09:00 Tue13:00 TueBoth at work
10:00 Tue14:00 TueBoth at work
11:00 Tue15:00 TueBoth at work
12:00 Tue16:00 TueBoth at work
13:00 Tue17:00 TueADT working
14:00 Tue18:00 TueADT working
15:00 Tue19:00 TueADT working
16:00 Tue20:00 TueADT working
17:00 Tue21:00 TueOff-hours both sides
18:00 Tue22:00 TueOff-hours both sides
19:00 Tue23:00 TueOff-hours both sides
20:00 Tue00:00 WedOff-hours both sides
21:00 Tue01:00 WedOff-hours both sides
22:00 Tue02:00 WedOff-hours both sides
23:00 Tue03:00 WedOff-hours both sides

Times computed for today in each zone using the IANA time zone database. The conversion accounts for daylight saving time wherever applicable.

About these time zones

Atlantic Daylight Time (ADT)
IANA identifier
America/Halifax
Current UTC offset
UTC-03:00
Current abbreviation
ADT
Major cities in this zone
Halifax
Greenwich Mean Time (GMT)
IANA identifier
Europe/London
Current UTC offset
UTC+01:00
Current abbreviation
GMT+1
Major cities in this zone
LondonManchesterEdinburghBirmingham

Sun today in Halifax and London

London
Sunrise
05:13
Sunset
20:43
Solar noon
12:58
Daylight
15h 29m

Related converters

GMT to ADT (reverse)ADT to ESTADT to PSTADT to UTCADT to CETADT to ISTEST to GMTPST to GMTUTC to GMTCET to GMTIST to GMT
Looking for local time? See time in Halifax or time in London.

Frequently asked questions

What is the time difference between ADT and GMT right now?+
GMT (Greenwich Mean Time) is currently 4 hours ahead ADT (Atlantic Daylight Time). The exact difference can change when one or both zones transition into or out of daylight saving time.
Does ADT or GMT observe daylight saving time?+
ADT: observes daylight saving time. GMT: observes daylight saving time.
When is the best time to schedule a meeting between ADT and GMT?+
The strongest overlap is 09:00–12:00 ADT (13:00–16:00 GMT), giving 4 hours when both sides are within standard 9am-5pm working hours.
What time is it in London when it is 12:00 noon in Halifax?+
When it is 12:00 Tue in Halifax (ADT), it is 16:00 Tue in London (GMT).
Which IANA time zone identifiers are used for ADT and GMT?+
ADT maps to "America/Halifax" in the IANA database. GMT maps to "Europe/London". These identifiers are what most software libraries use to convert times accurately, including DST handling.
Is Halifax ahead of or behind London?+
Whether Halifax (ADT) is ahead of or behind London (GMT) depends on the current UTC offsets. Right now GMT is 4 hours ahead ADT. The live converter and side-by-side clocks above always reflect the current direction.
What are the current UTC offsets for ADT and GMT?+
ADT is UTC-03:00 (ADT) and GMT is UTC+01:00 (GMT+1). Both offsets shift by one hour when the corresponding region enters or exits daylight saving time, so the live values on this page are the source of truth.
Can I schedule meetings during business hours for both ADT and GMT?+
Yes. There are 4 hours of overlap during standard 9am-5pm working hours, with the strongest window at 09:00–12:00 ADT.