Wake at 4:30 am
Four bedtimes, each one a whole number of sleep cycles before the alarm, with a quarter of an hour allowed for actually falling asleep.
Go to bed at 8:45 pm
5 cycles and 7h 30m asleep: the row nearest eight hours.
| Get into bed | Cycles | Time asleep |
|---|---|---|
| 7:15 pm | 6 cycles | 9h |
| 8:45 pm | 5 cycles | 7h 30m |
| 10:15 pm | 4 cycles | 6h |
| 11:45 pm | 3 cycles | 4h 30m |
7h 30m asleep
The night nearest eight hours, laid on a clock face.
The two assumptions
Move either one and every time above moves with it. The settings follow you around the site.
What a 4:30 am alarm asks of the evening
Half past four gives bedtimes of 7:15 pm, 8:45 pm, 10:15 pm and 11:45 pm. All four are on the evening before, and the three-cycle row, four and a half hours asleep, is the last one before midnight.
This is the alarm of the early shift on the planner: a 6:00 am start, less the hour and a half the planner allows for getting ready and getting there. The same page says what the rest of that day looks like, and the rota planner lays it out across a run of earlies and days off.
In London, New York, Johannesburg, Cape Town and Sydney a 4:30 am alarm is dark on every day of the year. London comes closest, with the sun up a little over ten minutes after it in the middle of June.
The six-cycle bedtime of 7:15 pm is in daylight in London in 2026 from 29 March, when the clocks go forward, to the middle of September, and in New York from late March to early September. Cape Town has it light from early November to early March, and Sydney from late October to the middle of March. Johannesburg never does, because its sun never sets much after 7:00 pm. The five-cycle bedtime of 8:45 pm is light in London alone, from the middle of May to early August, and 10:15 pm is dark in all five cities all year.
Every row is in bed before the clocks change and the alarm comes after the change, so on the night they go forward each row is an hour shorter in bed than the table says, and on the night they go back an hour longer. In 2026 those nights are 29 March and 25 October in London, 8 March and 1 November in New York, and 4 October and 5 April in Sydney. In Johannesburg and Cape Town the table is exact every night.
Further afield, the northern cities get their summer mornings. A 4:30 am alarm is in daylight in Stockholm from early May to the end of July, and in Moscow for about the same twelve weeks. Helsinki and Oslo have it from about 20 May to 19 July. Tokyo, which keeps one clock all year and sits east of the meridian it is set by, has it for about six weeks from late May, and Copenhagen and Anchorage for about four weeks around midsummer. In Helsinki and Oslo even the four-cycle bedtime of 10:15 pm is still in daylight for about eight weeks from late May.
Sunrise and sunset: the NOAA solar equations, for each city centre in 2026, to the nearest minute.
Every time on this page comes from two numbers: a cycle of 90 minutes and 15 minutes between getting into bed and being asleep. Neither is a measurement of you. The reference pages say where each one comes from.
A quarter of an hour either way
If the alarm is set to something near but not exactly 4:30 am, the table for it is a page of its own.
The other direction
Already in bed and deciding when to set the alarm? The sleep-now page runs the same sum forwards from the time where you are.