Scheduling a call with someone in Tokyo, London and New York simultaneously? Booking a flight that crosses the date line? Time zones are simple in principle but cause millions of scheduling errors every day. Here's everything you need to know.
The world is divided into 24 primary time zones, each one hour apart. They're measured as offsets from UTC (Coordinated Universal Time) — the successor to GMT. UTC+0 is roughly the UK in winter. UTC+5:30 is India (which uses a half-hour offset). UTC-5 is US Eastern Standard Time.
When it's 12:00 UTC, it's 17:30 in India, 07:00 in New York and 21:00 in Tokyo.
Always convert to UTC first, then to the destination zone. It's easier to calculate: "New York is UTC-5, Tokyo is UTC+9 — the difference is 14 hours" than to try to remember what time it is wherever you are relative to wherever they are.
Most confusion about time zones comes from daylight saving time (DST). The US, most of Europe, Australia and others move their clocks forward by one hour in summer. But they don't all do it on the same date:
This means the offset between two time zones changes 2–4 times a year. A tool that shows live current times (like our timezone converter) is more reliable than memorised offsets.
20 world cities with live clocks. Convert any time between zones instantly.
Convert Time →The date line runs roughly along 180° longitude through the Pacific Ocean. Cross it heading west (e.g. flying from LA to Tokyo) and you lose a day — you might leave Monday and arrive Wednesday. Cross it heading east and you gain a day. This is why travellers on round-the-world trips can arrive before they left (by the calendar).