The Structure of International Time Zones & UTC Offsets
The globe is divided into 24 principal longitudinal standard time zones spaced approximately 15° apart, corresponding to the Earth's 24-hour axial rotation. All global civil time coordinates from UTC (Coordinated Universal Time), which aligns with the Prime Meridian passing through Greenwich, England.
Major Global Financial & Business Hub Offsets
| City / Region | Standard Time Zone | Standard UTC Offset | Daylight Saving Time (DST) |
|---|---|---|---|
| London, UK | GMT / BST | UTC +0 / UTC +1 | Yes (March to October) |
| New York, USA | EST / EDT | UTC -5 / UTC -4 | Yes (March to November) |
| Los Angeles, USA | PST / PDT | UTC -8 / UTC -7 | Yes (March to November) |
| Berlin / Paris | CET / CEST | UTC +1 / UTC +2 | Yes (March to October) |
| Dubai, UAE | GST | UTC +4 | No (Constant year-round) |
| Mumbai, India | IST | UTC +5:30 | No (Half-hour offset) |
| Singapore | SGT | UTC +8 | No (Constant year-round) |
| Tokyo, Japan | JST | UTC +9 | No (Constant year-round) |
| Sydney, Australia | AEST / AEDT | UTC +10 / UTC +11 | Yes (October to April - Southern Hemisphere) |
Frequently Asked Questions (FAQ)
Why do some countries use half-hour offsets (like India IST +5:30)?
Certain nations (including India, Iran, and parts of Australia) intentionally positioned their standard time midway between two standard meridian zones to center solar noon more evenly across their territory.
What is the best window for a US-East to Europe meeting?
New York (EDT) and London/Europe generally have an optimal overlap between 9:00 AM – 12:00 PM EST, corresponding to 2:00 PM – 5:00 PM in the UK.