Wake at 6:30 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 10:45 pm
5 cycles and 7h 30m asleep: the row nearest eight hours.
| Get into bed | Cycles | Time asleep |
|---|---|---|
| 9:15 pm | 6 cycles | 9h |
| 10:45 pm | 5 cycles | 7h 30m |
| 12:15 am | 4 cycles | 6h |
| 1:45 am | 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 6:30 am alarm asks of the evening
Half past six gives bedtimes of 9:15 pm, 10:45 pm, 12:15 am and 1:45 am. Two of the four rows are after midnight, so a phone that asks for a date wants the next day's date for those two.
In London a 6:30 am alarm is in daylight from early April to the middle of September, and for about the three weeks before the clocks go forward at the end of March. In New York it is light from early April to early September, for a few days in early March, and again for the first days of November after the clocks go back. Johannesburg has it from late August to the end of April, about eight months of the year, and Cape Town from late September to late February. In Sydney it is light from late August to the middle of February, and again for a month from the first Sunday of April, when the clocks go back.
The six-cycle bedtime of 9:15 pm is before sunset only in London, and only for about a month around the solstice, from 9 June to 10 July. New York's latest sunset of the year is 8:31 pm, so there every row on this page is a bedtime after dark.
The three-cycle bedtime of 1:45 am is missing in the UK on the last Sunday of March, and happens twice on the last Sunday of October. New York keeps it on its spring-forward night, because the American change is at 2:00 am, but loses an hour between it and the alarm. On the first Sunday of November, 1:45 am comes round twice there too.
In December the sun rises in London at about 8:00 am, an hour and a half after this alarm, and in Cape Town in late June at 7:52 am.
Further afield, Madrid is the outlier in Europe: its earliest sunrise of the year is 6:44 am, so a 6:30 am alarm there never rings in daylight, while in Berlin, on the same clock, it is light from early April to early September. Singapore is dark at this hour all year too, with sunrise between 6:46 am and 7:17 am. Tokyo has daylight at 6:30 am from the middle of February to the end of November. Nairobi, a degree south of the equator, has two stretches, from the end of August to early January and from the middle of April to the middle of June, because its sunrise moves by only half an hour across the whole year. Dubai has daylight at 6:30 am from the middle of March to early November, and Hong Kong for almost the same stretch. In Cairo it is light from late February to the end of August, then again from the end of October, when the clocks go back, to late November. Toronto has it from the middle of April to late August, a shorter run than New York's.
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 6:30 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.