Timezone Compare
Compare timezones with precision. Drag to scroll, add cities, and see the exact current time.
Understanding Time Zones
The world is divided into 24 primary time zones, roughly aligned with longitude and ideally spaced 15° apart (since Earth rotates 360° in 24 hours, or 15° per hour). In practice, political and geographic boundaries cause time zones to deviate significantly from this ideal — some countries like India (UTC+5:30) and Iran (UTC+3:30) even use 30-minute offsets. China spans five natural time zones but uses a single national time (UTC+8) for administrative simplicity.
UTC: The Universal Reference
UTC (Coordinated Universal Time) is the world's primary time standard and the basis for all time zones. It replaced Greenwich Mean Time (GMT) as the official standard in 1967, though both terms are commonly used interchangeably in everyday speech. All modern time zones are expressed as an offset from UTC — for example, New York is UTC-5 in winter and UTC-4 during Daylight Saving Time.
Daylight Saving Time (DST)
Daylight Saving Time is the practice of advancing clocks by one hour during summer months to make evenings lighter. DST is controversial — it creates widespread scheduling confusion, especially for international meetings — and several countries have eliminated it. Key facts:
- Not universal: Most of Africa, Asia, and parts of South America do NOT observe DST. Japan, China, India, and most of the Middle East have no DST.
- Different dates: The US and EU switch on different dates. The US "springs forward" on the second Sunday in March; Europe does so on the last Sunday in March. This creates a 2–3 week period twice a year where transatlantic time differences shift by one hour.
- Always use a tool: Never rely on mental math for international scheduling. Time zone tools account for DST automatically — the human brain does not.
Tips for International Meeting Scheduling
- Find the overlap: Look for the window where all participants are between core working hours (9am–6pm). This tool's visual grid makes overlap immediately obvious.
- Rotate the burden: If there is no convenient overlap, rotate who takes the early/late slot meeting to meeting so the same participants don't always sacrifice.
- Always specify the city, not just the offset: Say "New York time" or "London time," not "UTC-5." Offsets change with DST; the city reference doesn't change what you mean.
- Check in advance: Verify the time for meetings that are weeks away — DST transitions can catch you off guard. Book meetings with UTC anchors and convert from there.