London to Johannesburg
The clock moves whether or not you are ready for it. This works out by how much, and what a bedtime walked an hour a night would look like on the way there or once you arrive.
Johannesburg runs an hour ahead of London. To arrive already keeping Johannesburg hours, your bedtime has to move an hour earlier — from 10:00 pm to 9:00 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 | 9:00 pm | 5:30 am | −1h | 5:06 pm | 4:52 am |
The gap, and why it is two numbers
In January, Johannesburg runs 2 hours ahead of London. In July it runs an hour ahead. London puts its clocks forward for part of the year and Johannesburg does not, so a single figure would be wrong for months at a time. The planner above works from the difference on the date in its field.
What that asks of a bedtime
Taking the shorter way round the dial, the move is 2 hours earlier in January and an hour earlier in July. At the planner's usual step of an hour a night, that is 2 nights of shifting in January and 1 in July, either before you fly or after you land.
This is clock arithmetic and nothing else. It does not know how you sleep on aeroplanes, it makes no claim about how quickly anybody adjusts, and an hour a night is a step size rather than a finding. Shorten the step in the planner if a smaller one suits you.
Going back
The return leg has its own page: Johannesburg to London.
Once you are there
With the clocks settled, the ordinary question comes back: what time to go to bed for the alarm you have set. That is the wake-time pages, which count in cycles rather than in zones.