For most medicines, on the morning after the clocks change, take your dose at the usual time on the new clock. If you take it at 08:00, it is still 08:00.
What changes is the gap overnight. When the clocks go back you get an extra hour, so that one gap is an hour longer. When they go forward you lose an hour, so it is an hour shorter. Every gap after that is back to normal.
When the clocks change next
| Where | Date | Clocks |
|---|---|---|
| UK and EU | Sunday 25 October 2026 | Back one hour |
| Most of the US and Canada | Sunday 1 November 2026 | Back one hour |
| Most of the US and Canada | Sunday 14 March 2027 | Forward one hour |
| UK and EU | Sunday 28 March 2027 | Forward one hour |
| New Zealand, and New South Wales, Victoria, South Australia, Tasmania and the ACT | Sunday 4 April 2027 | Back one hour |
The change happens in the early hours of Sunday morning, so it falls inside the overnight gap for almost every schedule. Queensland, Western Australia and the Northern Territory do not change their clocks, and neither do most of Asia, Hawaii or most of Arizona.
What the overnight gap becomes
The gap that crosses the change is the only one affected. These are the real hours between the two doses either side of it, if you keep the same clock times.
| Schedule | Dose times | Doses either side of the change | Clocks go back | Clocks go forward |
|---|---|---|---|---|
| Once a day, morning | 08:00 | Saturday 08:00 to Sunday 08:00 | 25 hours | 23 hours |
| Once a day, evening | 21:00 | Saturday 21:00 to Sunday 21:00 | 25 hours | 23 hours |
| Twice a day | 08:00 and 20:00 | Saturday 20:00 to Sunday 08:00 | 13 hours | 11 hours |
| Every 8 hours | 08:00, 16:00 and 00:00 | Sunday 00:00 to Sunday 08:00 | 9 hours | 7 hours |
| Every 6 hours | 00:00, 06:00, 12:00 and 18:00 | Sunday 00:00 to Sunday 06:00 | 7 hours | 5 hours |
For a once-a-day medicine the change is one hour in 24, once. For most people that one-off hour does not matter. It takes a bigger share of a short interval, though: losing an hour from an every-6-hours gap leaves five.
Every 8 hours and other fixed intervals
There are two ways to handle an interval schedule across the change, and they give different clock times afterwards.
Keep the clock times. You take your doses at 08:00, 16:00 and 00:00 as usual, and the one gap across the change runs an hour long or short. From Sunday morning the pattern is exactly what it was. This is the easier one to remember, and it is what a reminder set for fixed clock times does.
Keep the real hours. You count eight real hours from the last dose before the change. After the clocks go back, eight hours on from midnight is 07:00 on the new clock, so your doses become 07:00, 15:00 and 23:00. After the clocks go forward they become 09:00, 17:00 and 01:00. You then stay on the new times or ease back to the old ones a little at a time.
If the label just says every 8 hours and nobody has told you the timing is critical, keeping the clock times is the usual choice. If your prescriber or pharmacist has told you the interval is strict, ask them which they want before the weekend of the change. The course end date calculator keeps real hours when a course runs across a clock change, and says so on the result, so you can see where the last dose falls.
A dose in the middle of the night
If one of your doses is due between about 01:00 and 03:00, look at that night in particular. The exact hour depends on where you live.
- When the clocks go back, an hour repeats. In the US and the UK that is 01:00 to 02:00, so a dose at 01:30 comes round twice. In Germany, France, Spain and most of central Europe it is 02:00 to 03:00. Take that dose once, the first time round.
- When the clocks go forward, an hour is skipped. In the US and most of central Europe that is 02:00 to 03:00, so a dose at 02:30 has no 02:30 that night. The real moment it would have been is 03:30 on the new clock. In the UK the skipped hour is 01:00 to 02:00.
Check what your reminder does that night rather than assuming, and set a one-off alarm if you are not sure.
The pill and other time-sensitive medicines
Contraceptive pills come with a window for a late pill. The NHS gives three hours for a traditional progestogen-only pill, 12 hours for desogestrel and 24 hours for drospirenone. A one-hour clock change is smaller than any of those windows, but the leaflet in your pack is what counts. Our birth control reminder post has more on choosing the time.
If you have been told a medicine is time-critical, ask the person who prescribed it how they want the change handled. It is a quick question, and asking a week ahead means you are not working it out at 2am.
Clock changes are not time zones
Flying to another time zone moves your day by several hours, and you may have been told to stay on home time or switch to local time. That is a different problem, and the time zone post covers it. For the clock arithmetic, the time zone dose planner shows where each dose lands in the new zone.
What Doz does
Doz sets each reminder for a clock time on a given day. On the Sunday after the change, an 08:00 reminder goes off at 08:00 on the new time, and there is nothing to change in the app. An every-8-hours schedule is stored as clock times too, so it follows the first approach above. If your pharmacist wants you to keep real hours across the change, set a one-off alarm for the doses that move.
Frequently Asked Questions
Do I take my medication an hour earlier or later when the clocks change?
Usually neither. Take it at the same time on the new clock. If you take it at 08:00, you take it at 08:00 on Sunday. The gap since your last dose is an hour longer when the clocks go back and an hour shorter when they go forward.
Does daylight saving time affect the birth control pill?
The clock change moves your dose by one hour in real time, once. The NHS gives a window of three hours for a traditional progestogen-only pill, 12 hours for desogestrel and 24 hours for drospirenone. Check the leaflet for your pack and ask a pharmacist if you are unsure.
What happens to an every 8 hours schedule when the clocks go back?
If you keep the same clock times, the gap from the midnight dose to the 08:00 dose is nine hours instead of eight, once. If you keep real hours instead, your doses move to 07:00, 15:00 and 23:00 on the new clock.
Will my phone reminders change by themselves?
A reminder set for a clock time, such as 08:00 every day, normally stays at that clock time after the change. Check any reminder due in the middle of the night on the night of the change.
The short version
Keep taking doses at the usual clock times. The one gap across the change is an hour longer when the clocks go back and an hour shorter when they go forward. For an every-8-hours schedule you can keep the clock times or keep the real hours, and if the interval is strict, ask your pharmacist which. Look at any dose due between about 01:00 and 03:00 that night.
Sources
- EUR-Lex: Directive 2000/84/EC on summer-time arrangements
- 15 U.S. Code § 260a: Advancement of time
- govt.nz: Daylight saving
- NSW Government: Daylight saving
- NHS: How to take the progestogen-only pill
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