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Sleeping around a twelve-hour night

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

Written . Updated . By the DuskDial team.

In bed at 8:00 am, 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 pm5 cycles3h 15m
2:15 pm4 cycles4h 45m
12:45 pm3 cycles6h 15m
11:15 am2 cycles7h 45m
Bedtime8:00 am
Wake up3:45 pm
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 pm, which is an hour and a half before you are due on, and count whole cycles back from there.

In bedCyclesTime asleep
9:45 am5 cycles7h 30m
11:15 am4 cycles6h
12:45 pm3 cycles4h 30m
2:15 pm2 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 am until 12:45 pm, then again at 2:15 pm until 5:30 pm, with 1h 30m awake in between.

Twelve-hour nights across the year

A twelve-hour night starts in daylight for five to six months of the year in four of these five cities. In London in 2026 that runs from the clocks going forward on 29 March to about 22 September. In New York it runs from the middle of March to the middle of September. Cape Town has it from the middle of October to the middle of March, and Sydney from early October to late March. Johannesburg is the exception. Its latest sunset of the year is 7:05 pm, so a 7:00 pm start is light there only from about 23 December to 1 February.

It ends at 7:00 am, which is light all year in Johannesburg, whose latest sunrise is 6:56 am. In Sydney a 7:00 am finish is light on all but about four weeks of the year. In London it is light from late February to the start of October. It is then dark for the three weeks before the clocks go back on 25 October 2026, and light again for eleven days after. New York has the same shape around its own change on 1 November. Cape Town has light finishes from early September to early April.

With twelve hours between shifts, the sums are tight. Five cycles straight after clocking off run from 8:00 am to 3:45 pm. That leaves three and a quarter hours before the next start. The 3:45 pm alarm is in daylight in all five cities on every day of the year, even in London, where the earliest sunset is 3:51 pm. Split as three cycles after and two before, the day leaves an hour and a half awake in the middle, from 12:45 pm to 2:15 pm.

Twelve-hour nights take the clock changes too. On the night the clocks go back the shift is thirteen hours, and on the night they go forward, eleven. In 2026 those nights are 25 October and 29 March in London, 1 November and 8 March in New York, and 5 April and 4 October in Sydney. In Johannesburg and Cape Town every one is twelve hours.

The alarm before the shift is 5:30 pm. In Cape Town it goes off in daylight on every day of the year, because the earliest sunset there is 5:44 pm. In Johannesburg it does so on every day except from about the middle of May to early July. London has it light from late February to 24 October in 2026, the day before its clocks go back.

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.