Correction: the time zone overlap tool counted half-hour time zones in whole hours
· Correction · Time zone overlap calculator
Until October 13, 2026, the time zone overlap tool worked in whole hours of the first city. When the second city's clock was not a whole number of hours away, the tool counted an hour as shared even where only part of it was, and it printed times that do not exist on a clock. That was wrong. Mumbai, on UTC+5:30, is the one city in the tool's list this applies to.
The example is London and Mumbai, both working from 09:00 to 17:00, with the clocks as they stood on October 12, 2026, when Mumbai was 4.5 hours ahead of London. For each weekday the tool gave 4 hours of overlap, London 09:00-13:00 against Mumbai 13.5:00-17.5:00. The shared time is 3.5 hours, London 09:00-12:30 against Mumbai 13:30-17:00, and that is what the tool gives now.
Two cities a whole number of hours apart were not affected: for those the tool gives what it gave before. No business-day count and no date on this site changed.
This entry rests on this site's own code and on the tool as read in a browser before and after the correction. The two cities' clock offsets on the example date come from the time zone data of the system that builds this site. No document of an outside authority is cited.
Pages affected: Time zone overlap calculator