Moving a bedtime across zones
Two questions, one sum. What time your usual bedtime becomes where you are going, and how many nights of shifting an hour it takes to get there — worked either in the nights before you fly or in the nights after you land.
London runs an hour behind Johannesburg. To arrive already keeping London hours, your bedtime has to move an hour later — from 10:00 pm to 11:00 pm, on your own clock at home. That is one night, so the table below starts one night before you fly.
| Night | Bed | Up | Moved | Sunset there on this clock | Sunrise there on this clock |
|---|---|---|---|---|---|
| Night 1 | 11:00 pm | 7:30 am | +1h | 7:50 pm | 7:55 am |
Before or after
Shifting before you fly is done on your own clock at home: your bedtime walks towards what it will need to be, so that you land already keeping local hours. Shifting after you land is done on the local clock: you arrive still keeping home hours, and the plan walks your bedtime to the local one from there.
Both finish in the same place. The difference is which side of the flight you spend the nights on, and only one of the two has you arrive already keeping local hours.
The shorter way round
A day on the clock has twenty-four hours and no ends, so a nine-hour move east is also a fifteen-hour move west, and the planner always takes whichever is shorter. It is why a flight to Auckland can ask for fewer nights than the raw difference suggests.
The same sum with a one-hour gap is the night the clocks go forward, which the clock-change planner works for March 2027.
Clock arithmetic only. Nothing here is a claim about how fast anybody adjusts, and an hour a night is a step size this site picked because it divides neatly, not a finding about bodies. Set it to half an hour if you would rather go slowly.
Routes with their own page
- Johannesburg to London
- London to Johannesburg
- Cape Town to London
- London to Cape Town
- Johannesburg to Dubai
- Johannesburg to New York
- Johannesburg to Sydney
- Johannesburg to Amsterdam
- London to New York
- New York to London
- London to Dubai
- London to Singapore
- London to Sydney
- London to Hong Kong
- London to Tokyo
- London to Los Angeles
- London to Delhi
- London to Toronto
- London to Cairo
- New York to Los Angeles
- New York to Paris
- New York to Tokyo
- New York to Sao Paulo
- New York to Dubai
- Los Angeles to New York
- Los Angeles to Tokyo
- Los Angeles to Sydney
- Los Angeles to London
- Sydney to London
- Sydney to Los Angeles
- Sydney to Singapore
- Sydney to Auckland
- Dubai to London
- Dubai to Sydney
- Dubai to New York
- Singapore to London
- Tokyo to London
- Tokyo to Los Angeles
- Delhi to London
- Mumbai to Dubai
- Toronto to London
- Sao Paulo to London
Anywhere else
The planner above knows 89 cities. Only the busiest routes have a page of their own: a page for every pair would be 7,832 of them, and nearly all would be pages nobody ever asked for.