London to Delhi
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.
Delhi runs 4 and a half hours ahead of London. To arrive already keeping Delhi hours, your bedtime has to move 4 and a half hours earlier — from 10:00 pm to 5:30 pm, on your own clock at home. That is 5 nights, so the table below starts 5 nights 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 | 1:48 pm | 1:40 am |
| Night 2 | 8:00 pm | 4:30 am | −2h | 1:47 pm | 1:40 am |
| Night 3 | 7:00 pm | 3:30 am | −3h | 1:46 pm | 1:41 am |
| Night 4 | 6:00 pm | 2:30 am | −4h | 1:44 pm | 1:41 am |
| Night 5 | 5:30 pm | 2:00 am | −4.5h | 1:43 pm | 1:42 am |
The gap, and why it is two numbers
In January, Delhi runs 5 and a half hours ahead of London. In July it runs 4 and a half hours ahead. London puts its clocks forward for part of the year and Delhi 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 5 and a half hours earlier in January and 4 and a half hours earlier in July. At the planner's usual step of an hour a night, that is 6 nights of shifting in January and 5 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.
London to Delhi through the year
London to Delhi is five and a half hours forward in the northern winter and four and a half in the summer. India keeps a single clock all year, five and a half hours ahead of Greenwich, so the gap moves only when Britain changes its clocks, on the last Sundays of March and October.
Because the Indian clock is set on the half hour, a plan at an hour a night ends on a half step. In January the planner gives six nights, five of an hour and a last one of thirty minutes; in July, five nights, the last of thirty minutes.
By the sun, Delhi is about five hours and nine minutes ahead of London, since it lies 77 degrees further east. Mumbai, on the same clock but four degrees further west, is about four hours and fifty-two minutes ahead by the sun. The two cities are about 6,710 km apart on the great circle.
Going east, the move is earlier. A 10:00 pm bedtime in London is 3:30 am in Delhi in winter and 2:30 am in summer. Before you fly in January, the plan brings bedtime forward until it reaches 4:30 pm on London's clock, which is 10:00 pm in Delhi. From 6:30 pm in London in winter, or 7:30 pm in summer, it is already the next day in Delhi. Delhi's latest sunrise, 7:15 am in January, is 1:45 am in London.
Because the gap is never a whole number of hours, a London time on the hour is always half past the hour in Delhi. India's single clock spans about 29 degrees of longitude, so by that one clock the sun rises nearly two hours earlier in the far east of the country than in the far west. Nepal, next door, sets its clock at five and three quarter hours ahead of Greenwich, fifteen minutes ahead of India's. Delhi's earliest sunrise, 5:23 am in June, is 12:53 am in London, and its latest sunset, 7:23 pm in late June, is 2:53 pm. After you land in January, the plan starts from 3:30 am local time, the hour a London bedtime reads there, and comes back to 10:00 pm over six nights.
Going back
The return leg has its own page: Delhi 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.