Time tools look simple and are full of traps. A countdown that counts screen refreshes drifts the moment you switch tabs; a time zone conversion that ignores daylight saving is wrong for half the year — and wrong by a different amount during the weeks when North America and Europe change their clocks on different dates. The tools on this page are built to avoid both traps: timers are computed from your device's clock so they stay accurate in a background tab, and conversions use the full IANA time zone database built into your browser, the same data your phone and computer use to set their own clocks.
Everything runs locally in your browser. The world clock reads your own device's time zone setting to place "your location" in the list — that information never leaves your machine, and no account or download is needed for any tool here. If you need dates rather than hours, the age and date calculators linked above handle the arithmetic of days, weeks and years.