GMT and BST are the two clock settings used in the United Kingdom during different parts of the year. GMT, or Greenwich Mean Time, is UTC+00:00. BST, or British Summer Time, is UTC+01:00. When the UK moves to BST in spring, clocks go forward by one hour. When BST ends in autumn, clocks go back by one hour to GMT. GOV.UK confirms that UK clocks go forward on the last Sunday in March and back on the last Sunday in October.
In 2026, the UK changed from GMT to BST on March 29 and will return to GMT on October 25.
As of August 19, 2026, London and the rest of the UK are therefore on BST, UTC+01:00, not GMT.
If you need to convert UK time for a particular date, use the CurrentDateTime Time Zone Converter rather than assuming London is always on GMT.
GMT vs BST at a Glance
| Feature & Metric | GMT (Greenwich Mean Time) | BST (British Summer Time) |
|---|---|---|
| Full Name | Greenwich Mean Time | British Summer Time |
| UTC Offset | UTC+00:00 | UTC+01:00 |
| Setting Type | Standard-time period (Winter) | Summer-time period (DST) |
| Active Months | Commonly applies from late October to late March | Commonly applies from late March to late October |
| Offset Adjustment | No seasonal hour added | Clock is one hour ahead of GMT |
| Reference Time | 12:00 GMT = 12:00 UTC | 12:00 BST = 11:00 UTC |
The UK's National Physical Laboratory also distinguishes the two clearly. Its current schedules identify GMT as UTC and BST as UTC+1.
What Is GMT?
GMT stands for Greenwich Mean Time.
In modern UK civil-time use: GMT = UTC+00:00. So when the UK is on GMT, its civil clock has the same hour and minute as UTC.
For example:
| UTC (Universal Time) | GMT (Greenwich Mean Time, UTC+0) |
|---|---|
| 06:00 UTC | 6:00 AM GMT |
| 10:00 UTC | 10:00 AM GMT |
| 12:00 UTC | Noon GMT |
| 18:00 UTC | 6:00 PM GMT |
The UK's National Physical Laboratory operates the national time scale UTC, which contributes to international timekeeping.
GMT remains the UK's winter civil-time setting, even though modern precision timekeeping is based on UTC.
What Is BST?
BST stands for British Summer Time.
BST is: UTC+01:00. That means the UK clock is one hour ahead of GMT and UTC while BST is active.
For example:
| UTC (Universal Time) | BST (British Summer Time, UTC+1) |
|---|---|
| 06:00 UTC | 7:00 AM BST |
| 10:00 UTC | 11:00 AM BST |
| 12:00 UTC | 1:00 PM BST |
| 18:00 UTC | 7:00 PM BST |
The National Physical Laboratory confirms that UK civil time is UTC in winter and UTC+1 hour during summer time.
So BST does not mean that UTC itself changed. The UK's local clock moved one hour ahead of UTC.
What Is the Difference Between GMT and BST?
The difference is exactly one hour.
GMT = UTC+00:00
BST = UTC+01:00
Therefore: BST is one hour ahead of GMT.
For example: 9:00 AM GMT = 10:00 AM BST if you are comparing the two fixed clock references directly.
The UK does not use both simultaneously as its local civil time. It changes from one to the other depending on the season.
Which One Is the UK Using Right Now?
As of August 19, 2026, the UK is using British Summer Time.
London's current 2026 timezone schedule shows: BST = UTC+01:00, with the next change back to GMT on: October 25, 2026.
So if you are referring to London time during August 2026, the technically correct seasonal label is: BST, not: GMT. This is an important distinction for international meetings.
When Does BST Start in 2026?
In 2026, British Summer Time began on: Sunday, March 29, 2026.
At: 1:00 AM GMT, the clocks moved forward to: 2:00 AM BST.
GOV.UK lists March 29 as the 2026 spring clock-change date. Northern Ireland's official government information described the same 2026 transition: at 1:00 AM on March 29, clocks moved forward to 2:00 AM as the UK entered BST.
When Does BST End in 2026?
British Summer Time ends on: Sunday, October 25, 2026.
At: 2:00 AM BST, the clocks move back to: 1:00 AM GMT.
GOV.UK confirms October 25 as the 2026 autumn clock-change date. The practical sequence is: 1:59 AM BST, then: 1:00 AM GMT. The 1:00 AM hour occurs twice.
Why Does the UK Change Its Clocks?
The UK's seasonal clock change shifts an hour of usable daylight from the morning toward the evening during the warmer part of the year.
Historical records explain that BST begins when clocks go forward in spring and ends when clocks go back in autumn. The clock change does not create extra daylight. It changes how daylight is positioned relative to the civil clock.
So the underlying length of the day is not increased. Instead, the clock schedule changes. In summer, activities occur one clock hour earlier relative to the Sun than they would under GMT.
Does GMT Change Into BST?
It is often described that way in everyday conversation, but a more precise explanation is: the UK changes its civil-time setting from GMT to BST.
GMT itself does not suddenly become UTC+1. GMT remains: UTC+00:00, and BST remains: UTC+01:00. The United Kingdom switches which one it uses.
This distinction is useful because it prevents a common error: "GMT is UTC+1 during summer." That is incorrect. BST is UTC+1 during summer. GMT stays at UTC+0.
Is GMT Always UTC+0?
For the practical modern time-zone comparison covered here: GMT = UTC+00:00. That means there is no whole-hour offset between GMT and UTC. Timeanddate likewise notes that GMT has a zero UTC offset.
GMT and UTC are not technically identical concepts, however. UTC is the modern international time standard. GMT has historical roots in Greenwich mean solar time and remains a civil-time designation. For a deeper comparison, see UTC vs GMT: What Is the Difference?
Is BST Always UTC+1?
Yes. British Summer Time is: UTC+01:00.
The abbreviation does not mean a flexible UK timezone that changes its own offset. When BST is in use, the UK is one hour ahead of UTC. When the UK returns to UTC+00:00, it is using GMT instead. NPL's official material explicitly describes BST as UTC+1.
Does London Use GMT All Year?
No. This is one of the most common UK time mistakes.
London uses:
- GMT during the standard-time period (Winter)
- BST during the summer-time period (Summer)
Timeanddate explicitly warns that the UK is not on GMT all year and uses BST during the daylight-saving period. So a website that labels August London time as: GMT is technically wrong. In August 2026: London = BST = UTC+01:00.
Why People Still Say "GMT" in Summer
GMT is strongly associated with Britain, London, and Greenwich, so people sometimes use "GMT" casually to mean UK time throughout the year. That may work in informal local conversation. It becomes risky when someone overseas converts the time literally.
Suppose an event in London during August is advertised as: 3:00 PM GMT. Taken literally, that means: 15:00 UTC. But if the organizer really means: 3:00 PM London local time, in August 2026, London is on BST: 15:00 BST = 14:00 UTC. That is a one-hour difference.
This is why international schedules should use the correct seasonal designation or a geographic location.
Better Than GMT or BST: Use "London Time" for Recurring Events
Suppose a business runs a weekly call at: 10:00 AM London time throughout the year.
If you write: 10:00 AM GMT for every meeting, the schedule will not correctly represent summer London time. If you write: 10:00 AM BST all year, the winter schedule will be wrong.
For year-round local schedules, use: 10:00 AM London time and create the calendar event using the geographic timezone: Europe/London. That lets date-aware software apply GMT or BST automatically.
Why Geographic Time Zones Are Safer
A geographic timezone can carry rules associated with a location. For example: Europe/London can represent GMT during one part of the year and BST during another depending on the date. A fixed abbreviation such as GMT cannot do that.
This matters particularly for:
- recurring meetings
- calendars
- travel schedules
- booking systems
- software
- future events
For a specific event, use the CurrentDateTime Time Zone Converter and choose the actual date.
How the Spring Clock Change Works
When BST begins: 1:00 AM GMT → 2:00 AM BST. That means one local clock hour is skipped.
The sequence looks like: 12:58 AM GMT, 12:59 AM GMT, 2:00 AM BST, 2:01 AM BST. There is no local 1:30 AM during that spring transition. NPL confirms that UK clocks go forward at 1:00 AM UTC on the last Sunday in March.
How the Autumn Clock Change Works
When BST ends: 2:00 AM BST → 1:00 AM GMT. The local 1:00 AM hour occurs twice.
For example: 1:30 AM BST and later: 1:30 AM GMT look identical if you omit the timezone. But they are two different global instants. This matters for:
- server logs
- transport data
- transaction timestamps
- shift records
- scheduled jobs
Storing a UTC timestamp or explicit offset prevents that repeated-hour ambiguity.
Does the UK Gain an Hour in October?
People often say: "We gain an hour." What actually happens is that the local clock repeats an hour. When BST ends: 2:00 AM becomes 1:00 AM. So there are 25 local clock hours across that civil day. That is why people often describe the autumn transition as getting an extra hour. The opposite happens in spring, when a local clock hour is skipped.
Does the UK Lose an Hour in March?
In local-clock terms, yes. When the UK moves from 1:00 AM GMT to 2:00 AM BST, the civil day contains one fewer displayed hour.
This is commonly summarized as: spring forward and fall back. The actual passage of physical time continues normally. As NPL puts it, time itself is not changing, but the clocks and devices change between standard time and BST.
GMT vs BST Conversion Examples
Direct fixed-offset comparison:
| GMT (Standard Time, UTC+0) | BST (Summer Time, UTC+1) | Mathematical Difference |
|---|---|---|
| 6:00 AM | 7:00 AM | +1 Hour Ahead |
| 8:00 AM | 9:00 AM | +1 Hour Ahead |
| 10:00 AM | 11:00 AM | +1 Hour Ahead |
| 12:00 PM | 1:00 PM | +1 Hour Ahead |
| 3:00 PM | 4:00 PM | +1 Hour Ahead |
| 6:00 PM | 7:00 PM | +1 Hour Ahead |
| 11:00 PM | 12:00 AM next day | +1 Hour Ahead (Next Day) |
To convert: GMT → BST: add 1 hour; BST → GMT: subtract 1 hour. But remember that when converting an actual London event, you do not choose GMT or BST arbitrarily. The event date determines which local UK setting applies.
UK Time and New York
For much of the year, London and New York are commonly five hours apart. For example, during August 2026: London = BST, UTC+01:00; New York = EDT, UTC-04:00. Difference: 5 hours (London is ahead).
However, the United States and United Kingdom do not always change clocks on the same dates. That can temporarily change the normal difference.
Why London and New York Can Temporarily Become Four Hours Apart
The U.S. and UK follow different DST transition schedules. In 2026, participating U.S. locations began DST on March 8, while the UK moved to BST on March 29. GOV.UK confirms the March 29 UK date.
During the gap: New York had already moved to EDT at UTC-04:00, while London was still on GMT at UTC+00:00. Difference: 4 hours. After London entered BST: London = UTC+01:00, New York = UTC-04:00, and the difference returned to 5 hours. This is why recurring U.S.-UK meetings sometimes shift by one hour for a few weeks.
The Autumn Gap Can Cause the Same Problem
The regions also return to standard time on different dates. The UK returns to GMT on October 25, 2026. Participating U.S. locations return to standard time later in the autumn under the U.S. schedule. During the gap, the normal U.S.-UK time difference can temporarily change again. This is why you should never calculate a November international meeting using an August time difference.
UK Time and India
India Standard Time is: UTC+05:30.
During British Summer Time: UK = UTC+01:00, and India is 4 hours 30 minutes ahead.
During GMT: UK = UTC+00:00, and India is 5 hours 30 minutes ahead.
India's clock did not need to change for this difference to move. The UK changed its UTC offset by one hour. This is exactly the kind of seasonal international scheduling problem a date-aware converter solves.
UK Time and Pakistan
Pakistan Standard Time is: UTC+05:00.
During BST: UK = UTC+01:00, and Pakistan is 4 hours ahead.
During GMT: UK = UTC+00:00, and Pakistan is 5 hours ahead.
So a London meeting that stays fixed at 9:00 AM local time may appear one hour later in Pakistan once the UK returns from BST to GMT.
Why Your International Meeting May Move by One Hour
Imagine a recurring meeting at: 10:00 AM London time. During BST, that is: 09:00 UTC. After London returns to GMT: 10:00 AM London = 10:00 UTC. If the other participant's country does not make the same clock change, their meeting moves by one hour. This is not a calendar error. It is the natural result of London changing from UTC+1 to UTC+0.
Recurring Meetings Need Special Attention
A one-time event in August is relatively easy. London is on BST. A recurring event from August through December crosses the October clock change. You need to decide what should remain fixed.
- Keep London time fixed: The meeting remains 10:00 AM London. Other countries may see their local meeting time move.
- Keep UTC fixed: The meeting remains at one UTC instant. London's local display moves when it switches from BST to GMT.
These are different scheduling intentions. Choose deliberately.
What Should You Write in an International Invitation?
For a one-time summer event: Tuesday, August 25, 2026 at 3:00 PM BST (UTC+01:00) is precise.
For a winter event: Tuesday, December 15, 2026 at 3:00 PM GMT (UTC+00:00) is precise.
For a recurring event tied to the UK local clock: 3:00 PM London time is usually more useful, provided the calendar stores Europe/London.
Use PT, ET and London Time Carefully Together
International teams sometimes write "9 AM ET / 2 PM GMT" throughout the year. That can become wrong because neither New York nor London necessarily stays on the same fixed abbreviation throughout the year. A better calendar-based approach is: "9 AM New York / London local equivalent" for the chosen date. Then let geographic timezone rules calculate the actual relationship.
GMT vs BST for Flights and Travel
Travelers should pay attention to the date printed on tickets and itineraries. A summer London departure occurs under BST. A winter London departure occurs under GMT. Airline and booking systems normally handle this through geographic time-zone data, but manually converting the time using the wrong offset can create a one-hour error. Always convert: city + date + time rather than only: GMT + time.
GMT vs BST for Online Events
This matters for: webinars, livestreams, game releases, ticket sales, online courses, product launches, and conference sessions. If a July webinar hosted in London is advertised as 6 PM GMT, international participants may interpret that literally as UTC+0. But London's local clock in July is on BST, UTC+1. If the organizer actually means 6 PM London local time, the correct designation is: 6 PM BST. That one-letter difference can determine whether hundreds of participants arrive an hour early or late.
GMT vs BST for Developers
Developers should generally avoid hard-coding GMT when the application really means local civil time in London. Use a geographic timezone such as Europe/London. Then timezone data can choose GMT or BST according to the timestamp. A fixed offset such as +00:00 cannot automatically become +01:00 in summer. This is especially important for recurring schedules.
GMT vs BST in Server Logs
For technical logs, UTC is usually easier to work with than changing local UK time. Why? UTC does not make the UK's seasonal one-hour jump. A server can store 14:30 UTC while an application displays 3:30 PM BST during summer. In winter, the same UTC hour would display differently under GMT. Keeping the stored instant separate from local presentation avoids repeated or missing local-time hours around DST transitions.
How Your Phone Knows When to Change
Modern phones and computers generally use maintained geographic timezone data. If the device is configured for the UK, it knows that the local timezone changes according to the applicable rules. That is why many phones automatically move 1:00 AM → 2:00 AM when BST begins. Manual clocks, ovens, car dashboards, or older devices may still need to be adjusted yourself. NPL notes that the UK's national time signal provides UK civil time based on UTC, and its resources explain the seasonal clock-change schedule.
Does Northern Ireland Use the Same GMT and BST Rules?
Yes, Northern Ireland follows the UK's seasonal clock change between GMT and BST. Northern Ireland's official government information describes the same spring transition from 1:00 AM GMT to 2:00 AM BST. That means UK civil-time conversion should not treat Northern Ireland as following the Republic of Ireland's terminology, even though the island shares seasonal clock timing.
BST vs Irish Standard Time
This can be confusing because the Republic of Ireland uses different terminology. During summer: the UK uses BST = UTC+01:00, while Ireland uses Irish Standard Time = UTC+01:00. Their clocks can therefore show the same local time even though the timezone names differ. During winter, both are generally on GMT, UTC+00:00. This is a good reminder that matching clock offsets do not always mean matching terminology.
Europe/London or Europe/Belfast for automatic DST transitions.
Common GMT and BST Mistakes
GMT is UTC+00:00. BST is UTC+01:00. BST is therefore one hour ahead of GMT. NPL's official UK time material confirms GMT as UTC and BST as UTC+1.
As of August 19, 2026, the UK is on BST, UTC+01:00. London returns to GMT on October 25, 2026.
BST began on March 29, 2026. At 1:00 AM GMT, UK clocks moved forward to 2:00 AM BST.
BST ends on October 25, 2026. The clocks move back from 2:00 AM BST to 1:00 AM GMT.
No. London uses GMT during the standard-time period and BST during summer time.
They show the same ordinary clock reading at a zero offset, but they are technically different concepts. UTC is the modern international time standard, while GMT has a historical astronomical and civil-time role.
Yes. BST is the UK's summer-time or daylight-saving setting, one hour ahead of GMT.
BST is one hour ahead of GMT. In spring the UK moves its clocks forward one hour to enter BST.
Usually because London switched between GMT and BST while your own timezone either did not change or changed on a different date.
For a fixed winter event, GMT may be correct. For a year-round recurring London meeting, use the geographic timezone Europe/London or "London time" rather than hard-coding GMT.
The Rule to Remember
The simplest way to understand GMT vs BST is:
GMT = UTC+00:00
BST = UTC+01:00
The UK uses GMT during standard time and BST during summer time.
In 2026: BST began March 29, and GMT returns October 25.
As of August 19, 2026, UK local time is therefore BST.
If you are scheduling a meeting, flight, deadline, or online event, do not assume the UK is always on GMT. Use the actual date with the CurrentDateTime Time Zone Converter, or check the specific UK city through the CurrentDateTime World Clock.
The most reliable rule is: use London + date, not a memorized GMT offset.
