How this world clock works
Each city is tied to an IANA timezone name. Your browser converts the current instant into that zone, so London and New York stay correct when clocks change for daylight saving.
FAQ
Why is my city missing?
This starter lists a short set of cities. More zones can be added later without changing how the clock runs.
Is this using a time API?
No. Conversion is done in the browser from your device’s clock.