Timezone Converter

Understanding timezones

Timezones divide the world into regions that observe the same standard time. In theory, each timezone spans 15 degrees of longitude (360° / 24 hours = 15° per hour). In practice, timezone boundaries follow political borders, creating irregular shapes.

Most timezones are defined as offsets from Coordinated Universal Time (UTC). For example:

• UTC+0 - London (GMT)
• UTC+10 - Sydney (AEST)
• UTC-5 - New York (EST)
• UTC+5:30 - India (IST)

UTC vs GMT

UTC (Coordinated Universal Time) is the modern time standard. It’s based on atomic clocks and doesn’t observe daylight saving.

GMT (Greenwich Mean Time) was the historical standard based on solar time at the Royal Observatory in Greenwich. Today, GMT is effectively equivalent to UTC in practice.

For technical applications, always use UTC. It’s unambiguous and doesn’t change with seasons.

Daylight saving time

Many regions adjust clocks forward in spring and back in autumn, creating temporary timezone shifts:

Not all regions observe daylight saving. Queensland, Arizona, and most of Asia stay on standard time year-round.

Common timezone abbreviations

Abbreviations can be ambiguous -CST means both China Standard Time and Central Standard Time (US). Always specify the region or use UTC offsets when clarity matters.

International date line

The International Date Line runs roughly along the 180° meridian in the Pacific Ocean. Crossing it westward skips a day forward; crossing eastward repeats a day.

This creates interesting situations:

• When it’s Monday morning in Sydney, it’s still Sunday afternoon in Los Angeles
• Samoa switched from UTC-11 to UTC+13 in 2011, skipping December 30th entirely

Scheduling across timezones

Find overlapping work hours - Most business communication happens during working hours. For Sydney and London, the overlap is early morning AEDT / late evening GMT.

Use a reference timezone - Team agreements like “all deadlines are in UTC” prevent confusion.

Share timezone-aware links - Tools that automatically convert to the viewer’s local time reduce errors.

Consider Fridays carefully - Your Friday afternoon is someone else’s Saturday morning.

Common conversions

Note: Offsets change when regions enter/exit daylight saving at different dates.

How this tool works

Select a time and timezone, then choose target timezones to see the converted times. The converter handles daylight saving transitions automatically. Powered by a QuantCDN Edge Function.