Understanding Time Zones
The world is divided into 24 primary time zones, each one hour apart, measured as an offset from Coordinated Universal Time (UTC). The UK uses Greenwich Mean Time (GMT, UTC+0) in winter and British Summer Time (BST, UTC+1) from late March to late October. When scheduling international meetings, it is essential to account for Daylight Saving Time (DST), which is observed at different times — or not at all — in different countries.
Key Time Zone Reference
| City | Time Zone | UTC Offset (Winter) | DST Observed |
|---|---|---|---|
| London | GMT/BST | UTC+0 | Yes (UTC+1 in summer) |
| New York | EST/EDT | UTC-5 | Yes (UTC-4 in summer) |
| Los Angeles | PST/PDT | UTC-8 | Yes (UTC-7 in summer) |
| Dubai | GST | UTC+4 | No |
| Mumbai | IST | UTC+5:30 | No |
| Singapore | SGT | UTC+8 | No |
| Tokyo | JST | UTC+9 | No |
| Sydney | AEST/AEDT | UTC+10 | Yes (UTC+11 in summer) |
What is UTC?
UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks and time. It is effectively the same as GMT but is more precisely defined. All time zones are expressed as UTC+ or UTC- offsets.
Why do some countries not observe DST?
Countries near the equator, such as Singapore, Dubai, and most of Africa, do not observe Daylight Saving Time because the variation in daylight hours throughout the year is minimal. DST was originally introduced in temperate regions to make better use of natural daylight during longer summer days.
How do I schedule a meeting across multiple time zones?
Use this converter to find a time that works in all relevant zones. Generally, the best overlap between the UK (GMT/BST), US East Coast (EST/EDT), and Asia-Pacific is early morning UK time (07:00–09:00 GMT), which corresponds to late evening in Asia and early morning in New York.