Clocks going back: resetting your heating timer
The clocks go back one hour at 2am on Sunday 25 October 2026. A thermostat connected to the internet takes its time from the network, so it looks after itself. A mechanical dial timer never does, and a digital programmer only does if its daylight saving setting is on. Anything that does not follow runs an hour early.
When do the clocks go back in 2026?
Sunday 25 October 2026. Gov.uk states the rule: "In the UK the clocks go forward 1 hour at 1am on the last Sunday in March, and back 1 hour at 2am on the last Sunday in October." Its table gives 2026 as 29 March forward and 25 October back. The same page names the two halves of the year: "The period when the clocks are 1 hour ahead is called British Summer Time (BST)", and "When the clocks go back, the UK is on Greenwich Mean Time (GMT)."
Nothing about your boiler changes that Sunday. What changes is the time your controls are measured against, and only some of them notice.
Which heating controls change themselves, and which do not
The clock does not live in the same box in every house. On a combi it usually sits in the programmer or the programmable thermostat. On an older system with a cylinder it is usually a twin channel programmer in the airing cupboard.
Smart thermostats: they take the time from the network
An internet-connected thermostat reads the time off the connection rather than a battery-backed clock. The Worcester Wave manual says it plainly where it covers a power cut: "Date and time are automatically synchronised." If your control has an app and a live connection you should not have to touch it. If it still shows the wrong hour on Monday, check the Wi-Fi.
Digital programmers: it depends on one hidden setting
A digital time control adjusts itself only if it has been told to. Worcester Bosch's Greenstar Comfort I RF is a clear example. Its user menu carries a DST (Daylight Savings Time) setting, and the manual describes the choice: "if ON is selected the Programmer will automatically adjust the time in conjunction with daylight savings time". Turn it off, or have an installer hand the boiler over with it off, and the programmer sits on summer time all winter. That setting is the usual reason a new programmer sits on the wrong hour.
Mechanical dial timers: always by hand
A mechanical timer is a clock face with a ring of sliding tabs around the edge. It has no idea what month it is, so it never changes. Worcester still publishes a manual for one: the MT20 Wired Timer calls itself a "Single channel mechanical timer" on the cover of its own manual.
What to do, by control type
| Control type | Changes itself? | What you do on 25 October |
|---|---|---|
| Smart thermostat with an app (Wi-Fi connected) | Yes, from the network. | Nothing. Check the Wi-Fi if the hour looks wrong. |
| Digital programmer, daylight saving switched on | Yes, it adjusts itself. | Nothing. Check the display to confirm it did. |
| Digital programmer, daylight saving switched off | No. | Set it back an hour by hand, then turn the setting on for the spring. |
| Mechanical dial timer with sliding tabs | No. There is no calendar inside it. | Turn the outer ring clockwise to the right time. |
| Plain room thermostat, or a radiator valve | There is no clock in it. | Nothing. The timer is at fault, not this. |
| Boiler display showing a time | Depends on the programmer. | Treat it as the programmer above. |
Resetting a mechanical dial timer: turn it forwards, never backwards
This is the one that catches people out. When the clocks go back you want to wind the dial back an hour. On a mechanical timer, do not.
Worcester prints a warning against it in the MT20 manual under the heading "Risk of damage to mechanical clock": "The unit may be damaged if you rotate the outer ring anticlockwise." Its instruction is to "Only rotate the outer ring clockwise (direction shown on clock face)" until "the 24 hour pointer displays the correct time." So to lose an hour you go forwards twenty-three.
Leave the sliding tabs alone. On the MT20, Worcester states that "Each tappet represents 15 minutes", moved "inwards for ON periods" and "outwards for OFF periods". They are set against the dial, so once the pointer is right the programme is right again.
Check the mode selector. On the MT20 it offers OFF for "Constant off (no heating)", Timed, which "Switches between and uses both ON and OFF periods according to the tappets", and ON for "Constant on (available for a heating demand, in-conjunction with a room thermostat)". If the heating has been odd all week, someone may have knocked it off Timed.
Resetting a digital programmer
Every make words its menus differently, so read the guide for your model. The Comfort I RF shows the shape. Its clock sits under a Time/Date function in the user menu: select Time/date, press to enter the Clock time function, press again so the hours flash, turn to the correct hour, confirm, then set the minutes. The date follows the same rhythm. After the year, the manual has you "Turn the knob to display DST (Daylight savings time)" and choose ON or OFF.
Set the date as well as the time, because a programmer running a different schedule at weekends needs to know which day it is. Leave daylight saving on so next March looks after itself.
A programmer that has forgotten the time entirely is a different symptom. Worcester notes that the Time/Date function "would be used on initial set up of the Programmer or if the time and date were lost due to the boiler being switched off for an extended period of time".
Why the heating runs an hour out for the week afterwards
At 2am on 25 October the country steps back to 1am. A timer that does not follow now reads an hour ahead of the real world. When it believes it is 06:30 and fires the heating, the kitchen clock says 05:30.
It also takes the heating off an hour early, which is the half people actually notice: the house is cooling by the time everyone is up. In March it runs the other way. The change lands in the small hours of a Sunday, so it is often the following weekend before anyone looks at the dial.
The five-minute check on Sunday 25 October
One lap of the house while the kettle boils.
- Find the clock: the programmer by the boiler, the airing cupboard timer, or the wall thermostat, then compare its display with your phone. An hour out is the whole diagnosis.
- Mechanical dial: turn the outer ring clockwise only, never anticlockwise.
- Digital: correct the clock, set the date too, and leave daylight saving on.
- Check the mode switch is still on Timed.
- Book the annual service if it is due.
When the clock is right and the heating still is not
If the display reads the right time and the heating still arrives at the wrong hour, the fault has moved past the clock. Common candidates are a room thermostat that is not calling for heat, a wireless thermostat that has lost its receiver link, or a motorised valve that is not switching. Our guides to room thermostat problems and to a wireless thermostat not working, both linked at the foot of this page, work through those in order.
That is the point to call someone. Setting a clock and sliding a tab are homeowner jobs. Anything behind the boiler casing, at the gas valve, or in the wiring centre is not. For a thermostat, a receiver link or a motorised valve, book a repair and we will arrange an engineer to diagnose it. For anything at the gas valve or behind the casing, we work with a national network of thousands of Gas Safe registered engineers. Call 0333 772 6247, or use the Send us the details button on this page and we will come back to you.
One safety point overrides everything on this page. If you smell gas, do not touch any electrical switches, do not smoke, put out all naked flames, turn the gas off at the meter control valve if you know where it is and it is safe to do so, open the doors and windows, and contact the National Gas Emergency Service immediately on 0800 111 999.
Clocks going back and your heating: FAQs
When exactly do the clocks go back in 2026?
Sunday 25 October 2026. Gov.uk states that in the UK the clocks go forward 1 hour at 1am on the last Sunday in March, and back 1 hour at 2am on the last Sunday in October. Its table lists 2026 as 29 March forward and 25 October back. The UK is then on Greenwich Mean Time.
Does my boiler change its own clock when the clocks go back?
It depends on the control, not the boiler. An internet-connected smart thermostat takes its time from the network: the Worcester Wave manual says date and time are automatically synchronised. A digital programmer adjusts only if its daylight saving setting is on. A mechanical dial timer never changes.
My digital programmer did not change. Is it broken?
Probably not. Many programmers carry a daylight saving setting that can be switched off. On the Worcester Bosch Greenstar Comfort I RF you turn the knob to display DST and choose ON or OFF, and the manual says that if ON is selected the programmer will adjust the time in conjunction with daylight savings time. Set to OFF, it stays on summer time.
How do I put a mechanical dial timer back an hour?
You do not go back, you go forwards. Worcester warns in the MT20 Wired Timer manual that the unit may be damaged if you rotate the outer ring anticlockwise, and says to only rotate it clockwise. Turn it all the way round to the correct time. Leave the sliding tabs alone: they are set against the dial, so the programme is right once the pointer is.
Why does my heating come on an hour early after the clocks go back?
Because the timer did not move and the country did. At 2am the clocks went back to 1am, so a timer that stayed put now reads an hour ahead. When it thinks it is 06:30 and fires the boiler, it is really 05:30. It switches off an hour early too. In spring the fault runs an hour late instead.
Do I need to change my room thermostat or my radiator valves?
No. A plain room thermostat and a standard radiator valve have no clock in them, so there is nothing to reset. They decide how warm a room gets, not when the heating runs. If the heating arrives at the wrong hour, look at the timer instead.
The clock is right but the heating still will not come on. What now?
The fault is past the clock. Check the room thermostat is calling for heat and, on a wireless system, that it still has a link to its receiver. If not, book a repair and we will arrange an engineer to diagnose it. On a Smart Plan cover plan we aim to get an engineer out to you within two working days, and cover-plan call-outs run Monday to Friday, 08:00 to 18:00. A £95 call-out fee, paid in advance, applies in your first 30 days. Do not open the boiler casing. If you smell gas, call the National Gas Emergency Service on 0800 111 999.
Clock reset, boiler still misbehaving?
Send us the details and we will arrange a Gas Safe registered engineer to diagnose it. To spread the cost of the winter ahead, a Smart Plan boiler and central heating module pays parts and labour up to £500 in a 12-month period while your boiler is under 7 years old, or up to £200 once it is over 7. On the cover plan we aim to get an engineer out to you within two working days, and cover-plan call-outs run Monday to Friday, 08:00 to 18:00. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, no-access visits and early annual-service requests, and cover still applies during those 30 days. Once you use a service, a 12-month agreement period begins, and leaving early costs the remaining months or 75% of the outstanding balance. A one-off repair without a plan is booked and priced on its own separate terms, with appointments Monday to Friday, 09:00 to 17:00. Smart Plan is a service plan, not insurance, from UK Boiler Company Ltd, trading since 2014.
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