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Sleeping around a twelve-hour day

On at 7:00 am, off at 7:00 pm: 12h on shift and 12h between one ending and the next beginning.

Written . Updated . By the DuskDial team.

In bed at 8:00 pm, 1 hour after clocking off. The rows differ only in when you get up.

Sleeping after the shift
Up atCyclesUntil the next start
3:45 am5 cycles3h 15m
2:15 am4 cycles4h 45m
12:45 am3 cycles6h 15m
11:15 pm2 cycles7h 45m
Bedtime8:00 pm
Wake up3:45 am
121234567891011

7h 30m asleep

Five cycles taken straight after clocking off, laid on an ordinary clock face.

Sleeping before the shift

The same sum run the other way: be up at 5:30 am, which is an hour and a half before you are due on, and count whole cycles back from there.

In bedCyclesTime asleep
9:45 pm5 cycles7h 30m
11:15 pm4 cycles6h
12:45 am3 cycles4h 30m
2:15 am2 cycles3h

Splitting it in two

One block after clocking off and a second before clocking on. If the two will not fit between the shifts, the total below says so.

Both blocks together

7h 30m

In bed at 8:00 pm until 12:45 am, then again at 2:15 am until 5:30 am, with 1h 30m awake in between.

Twelve-hour days across the year

The alarm for a 7:00 am start is 5:30 am, and the 5:30 am wake page has its own daylight figures. The start itself is the moment a twelve-hour night ends. It is light on every day of the year in Johannesburg, and on all but about four weeks in Sydney. In London it is light from late February to the start of October, and in 2026 for eleven days after its clocks go back on 25 October. New York has it light from early February to early October, apart from the two weeks after its clocks go forward, on 8 March in 2026, and again through November. In Cape Town it is light from early September to early April.

The finish, at 7:00 pm, is the moment a twelve-hour night starts. In 2026 it is light in London from 29 March to about 22 September, and in New York from the middle of March to the middle of September. Cape Town has it light from the middle of October to the middle of March, and Sydney from early October to late March. In Johannesburg, where the sun never sets later than 7:05 pm, it is light only from about 23 December to 1 February.

Twelve hours between shifts leave five cycles straight after clocking off, from 8:00 pm to 3:45 am. That is three and a quarter hours before the next start. An 8:00 pm bedtime is still light in London from the middle of April to late August. In New York it is light from about 10 May to 11 August, and in Sydney from the middle of December to early February. Cape Town has it light for about two weeks around the new year, and Johannesburg never.

Both sleeps span the small hours, so both take the clock changes. Each is an hour shorter on the night the clocks go forward and an hour longer on the night they go back. In 2026 they are 29 March and 25 October in London, 8 March and 1 November in New York, and 4 October and 5 April in Sydney. Johannesburg and Cape Town have none.

Split as three cycles after and two before, the night leaves an hour and a half awake in the middle. That hour and a half runs from 12:45 am to 2:15 am.

Sunrise and sunset: the NOAA solar equations, for each city centre in 2026, to the nearest minute.

Cycles are 90 minutes here and dropping off takes 15, as on the rest of the site, and the next shift is taken to start at the same time the following day. Rows that will not fit between two shifts are marked. That is the only judgement on the page: which arrangement suits your rota and your household is not something this site can know.

The other rotas

A run of days and nights together, with the switch days between them, is laid out on the rota planner.