Compare two to four cities and see the fairest hour for a recurring call — the one that spreads the early starts and late nights, and how long it lasts before the clocks change.
Two-city time is easy; a recurring call across three or four is the hard part — no single hour sits inside everyone’s working day, so someone takes an early start or a late night. This planner finds the fairest slot (spreading that cost) and the most efficient one (least total), and shows on a live day/night map who sacrifices. The example below is New York, London and Mumbai; type your own cities to replace it.
The fairest recurring slot lands in around midday UTC. It sits close to the working day in all three cities — an unusually kind corridor, with no one pushed far past their hours. Spreading the load and minimising the total agree here, so there is no cheaper option that would not fall on one city. The exact time is computed live below and shifts by up to an hour around daylight-saving transitions.
This time holds steady through 20 Feb — the clock change on 25 Oct barely moves it.
Need a single instant instead of a recurring window? Convert a specific time between two of these cities.
Each city’s core day is 9:00–17:00 (zero cost). Outside it, an hour later hurts less than an hour earlier — staying online past five beats waking before eight — so the penalty curve is asymmetric. Fair minimises the worst-off city first (leximin); Efficient minimises the total. Both land on the working-hours frontier — Fair just refuses to let one city absorb the whole gap.