World Clock

Scheduling across time zones is exactly where mental arithmetic breaks down, mostly because half the world moves its clocks in summer and Brazil stopped doing that in 2019. This page shows the current time in ten cities (Sao Paulo, New York, London, Paris, Berlin, Tokyo, Sydney, Mumbai, Dubai and Mexico City), with the weekday and date, refreshing once a second.

Each card reads the browser own time zone database, the IANA one, so daylight saving comes and goes by itself with no table to maintain. That explains a detail people keep tripping over: the gap between Sao Paulo and New York is not fixed. It sits at 2 hours during the southern summer and drops to 1 hour once the US springs forward. Mumbai runs on a half-hour offset, UTC+5:30, and Sydney does daylight saving in the opposite season.

The time does not come from a time server: the page reads your device clock and applies each zone offset to it. If your machine is running two minutes late, all ten cards are two minutes late together, so it is worth checking that automatic date and time sync is on before you trust the seconds. The city list is fixed, with no way to add or remove one. Nothing is sent anywhere.