ClockTime zones
World clocks and civil-time conversion use the browser’s Intl.DateTimeFormat implementation and its installed IANA time-zone data. Rules can change, especially for future dates. Keep your browser and operating system updated. A city label identifies a time zone; we do not use a fixed UTC offset in place of seasonal rules.
The converter searches for the instants matching an entered local time. If none match, the time falls in a clock-change gap. If more than one matches, the user chooses the occurrence. Conversion is limited to 1900–2100.
Calendar calculations
Date tools use Gregorian calendar arithmetic independently of your local time zone. Calendar-day counts are not elapsed-hour measurements. Year and month additions clamp a missing day to the end of the target month before adding days.
Timers and clocks
World clocks, countdowns, and timers rely on your device’s wall clock. The stopwatch uses a monotonic clock for elapsed time. Browser throttling and device sleep affect when results are displayed; there is no server-backed alarm service.
Technical references
- Intl.DateTimeFormat — browser time-zone formatting
- IANA Time Zone Database
- Performance.now — monotonic elapsed time
Results are intended for everyday planning. Check authoritative local rules for historical or high-consequence uses.