Spring forward: trains running at 01:00 GMT disappear
On the last Sunday of March, 01:00 GMT becomes 02:00 BST instantly. Any train scheduled to depart between 01:00 and 01:59 GMT simply never runs.
National Rail handles this by holding overnight services before the change. A train due to leave at 00:30 GMT and arrive at 02:30 GMT will depart on time and arrive in BST without issue. But a train timed to depart at 01:15 GMT? It is cancelled. Passengers on these services are rebooked onto earlier or later departures.
The change occurs at 01:00 UTC (01:00 GMT) for a reason: most rail services have not started their Sunday morning runs, and the last pub customers have gone home. Disruption is confined to a narrow window of about 60 minutes.
Autumn back: the duplicate hour and how it is handled
When clocks go back on the last Sunday of October, 02:00 BST becomes 01:00 GMT. That means the hour from 01:00 to 01:59 GMT happens twice.
National Rail solves this by running the same schedule twice during the duplicate hour. A train scheduled to depart at 01:15 BST will depart at 01:15 GMT (first time) and again at 01:15 GMT (second time) after the clocks have gone back. In practice, stations announce both departures clearly, and real-time boards show the second run as "01:15 GMT (repeated)."
Overnight services that would have arrived at 02:00 BST arrive at 01:00 GMT instead, effectively giving passengers an extra hour. No cancellations, just a repeated set of departures.
When National Rail issues new schedules: May and December
Clock change nights are separate from the main schedule updates. National Rail refreshes its full service pattern twice a year: in May (summer schedule) and December (winter schedule). These updates shift service patterns, add or remove routes, and adjust frequencies.
The clock change itself does not trigger a new schedule. The spring clock change in March happens during the winter schedule period; the autumn change in October happens during the summer schedule period. Passengers should check their journey for the relevant schedule date, not the clock change date.
Night Tube on the London Underground through the clock change
The Night Tube runs Friday and Saturday nights on the Central, Jubilee, Northern, Piccadilly and Victoria lines. When a clock change falls on a Saturday night, the service continues through the transition.
Spring forward (March): the last train before 01:00 GMT arrives at its destination before the change. The next train after 01:00 BST departs as normal. There is a gap of about 60 minutes where no Night Tube trains run.
Autumn back (October): the Night Tube runs its full schedule through the duplicate hour. Trains scheduled for01:30 BST depart again at 01:30 GMT after the clocks go back. Passengers travelling between01:00 and 02:00 get two chances to catch their train.
Why do trains clock change UK at 01:00 UTC?
The 01:00 UTC change time was not chosen for astronomers or broadcasters. It was chosen for the railways.
By 01:00 UTC, most Sunday morning passenger services have not started. Freight trains that run overnight are already in sidings or on long-distance routes where a 60-minute adjustment is manageable. Pubs have closed (licensing hours end at 23:00 or midnight), so late-night revellers are not stranded.
The alternative, a midnight change, would have hit Friday and Saturday night services hard. A 02:00 change would have caught early Sunday commuter trains. The 01:00 UTC sweet spot keeps disruption to a single dead hour in spring and a repeated hour in autumn.