Time Zone Converter
Understanding Time Zones
Time zones are regions that observe the same standard time. The world is divided into 24 time zones, roughly 15 degrees of longitude wide, centered on the Prime Meridian at Greenwich, England (UTC/GMT).
Major Time Zone Offsets from UTC
| Time Zone | Abbreviation | UTC Offset | Major Cities |
|---|---|---|---|
| Pacific Time | PST/PDT | UTC-8/-7 | Los Angeles, San Francisco |
| Mountain Time | MST/MDT | UTC-7/-6 | Denver, Phoenix |
| Central Time | CST/CDT | UTC-6/-5 | Chicago, Houston |
| Eastern Time | EST/EDT | UTC-5/-4 | New York, Miami |
| Greenwich Mean Time | GMT | UTC±0 | London, Dublin |
| Central European Time | CET/CEST | UTC+1/+2 | Paris, Berlin, Rome |
| Japan Standard Time | JST | UTC+9 | Tokyo, Osaka |
| Australian Eastern | AEST/AEDT | UTC+10/+11 | Sydney, Melbourne |
Daylight Saving Time
Many countries observe Daylight Saving Time (DST), moving clocks forward by one hour in spring and back in fall. This affects time conversions seasonally:
- US DST: Second Sunday of March to first Sunday of November
- European DST: Last Sunday of March to last Sunday of October
- No DST: Japan, China, India, most of Africa, and others
Frequently Asked Questions
What is UTC?
UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. It's effectively the same as GMT but defined more precisely using atomic clocks. All time zones are expressed as offsets from UTC.
What time is it in New York when it's noon in London?
When it's 12:00 PM (noon) in London (GMT), it's 7:00 AM in New York (EST). New York is 5 hours behind London. During daylight saving time, the difference may be 4 hours.
What is the International Date Line?
The International Date Line is an imaginary line in the Pacific Ocean at roughly 180° longitude. When you cross it westward, you add a day; crossing eastward, you subtract a day. This prevents the accumulation of time differences when traveling around the world.
Why do some time zones have 30-minute offsets?
Some countries chose half-hour offsets to better align solar noon with clock noon. India (UTC+5:30), Iran (UTC+3:30), and parts of Australia use these non-standard offsets. Nepal even uses UTC+5:45!
How do I schedule a meeting across multiple time zones?
Find overlapping business hours (typically 9 AM - 6 PM) for all participants. For US-Europe calls, early morning US/afternoon Europe works best. For US-Asia, early morning US or late afternoon Asia is common.
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