GMT to ADT Time Converter

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

London · Greenwich Mean Time
01:06:23
Thursday, May 14, 2026
GMT+1 · UTC+01:00
Halifax · Atlantic Daylight Time
21:06:23
Wednesday, May 13, 2026
ADT · UTC-03:00

Convert a specific time

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

Daylight Saving status right now

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
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

When can GMT and ADT 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
GMT
ADT
Both zones in working hours (9am-5pm)
One zone working
Off-hours
Columns are hours of the day in London (GMT). 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: 13:00–16:00 GMT (09:00–12:00 ADT).

Hour-by-hour GMT to ADT conversion table

GMT time (London)ADT time (Halifax)Status
00:00 Thu20:00 WedOff-hours both sides
01:00 Thu21:00 WedOff-hours both sides
02:00 Thu22:00 WedOff-hours both sides
03:00 Thu23:00 WedOff-hours both sides
04:00 Thu00:00 ThuOff-hours both sides
05:00 Thu01:00 ThuOff-hours both sides
06:00 Thu02:00 ThuOff-hours both sides
07:00 Thu03:00 ThuOff-hours both sides
08:00 Thu04:00 ThuOff-hours both sides
09:00 Thu05:00 ThuGMT working
10:00 Thu06:00 ThuGMT working
11:00 Thu07:00 ThuGMT working
12:00 Thu08:00 ThuGMT working
13:00 Thu09:00 ThuBoth at work
14:00 Thu10:00 ThuBoth at work
15:00 Thu11:00 ThuBoth at work
16:00 Thu12:00 ThuBoth at work
17:00 Thu13:00 ThuADT working
18:00 Thu14:00 ThuADT working
19:00 Thu15:00 ThuADT working
20:00 Thu16:00 ThuADT working
21:00 Thu17:00 ThuOff-hours both sides
22:00 Thu18:00 ThuOff-hours both sides
23:00 Thu19:00 ThuOff-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

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

Sun today in London and Halifax

London
Sunrise
05:11
Sunset
20:44
Solar noon
12:58
Daylight
15h 32m

Related converters

ADT to GMT (reverse)GMT to ESTGMT to PSTGMT to UTCGMT to CETGMT to ISTEST to ADTPST to ADTUTC to ADTCET to ADTIST to ADT
Looking for local time? See time in London or time in Halifax.

Frequently asked questions

What is the time difference between GMT and ADT right now?+
ADT (Atlantic Daylight Time) is currently 4 hours behind GMT (Greenwich Mean Time). The exact difference can change when one or both zones transition into or out of daylight saving time.
Does GMT or ADT observe daylight saving time?+
GMT: observes daylight saving time. ADT: observes daylight saving time.
When is the best time to schedule a meeting between GMT and ADT?+
The strongest overlap is 13:00–16:00 GMT (09:00–12:00 ADT), giving 4 hours when both sides are within standard 9am-5pm working hours.
What time is it in Halifax when it is 12:00 noon in London?+
When it is 12:00 Thu in London (GMT), it is 08:00 Thu in Halifax (ADT).
Which IANA time zone identifiers are used for GMT and ADT?+
GMT maps to "Europe/London" in the IANA database. ADT maps to "America/Halifax". These identifiers are what most software libraries use to convert times accurately, including DST handling.
Is London ahead of or behind Halifax?+
Whether London (GMT) is ahead of or behind Halifax (ADT) depends on the current UTC offsets. Right now ADT is 4 hours behind GMT. The live converter and side-by-side clocks above always reflect the current direction.
What are the current UTC offsets for GMT and ADT?+
GMT is UTC+01:00 (GMT+1) and ADT is UTC-03:00 (ADT). 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 GMT and ADT?+
Yes. There are 4 hours of overlap during standard 9am-5pm working hours, with the strongest window at 13:00–16:00 GMT.