How the Time Zone Calculator Works
This tool calculates the time zone difference between two world cities, showing UTC offsets and the direction of the difference. It is useful for planning international calls, video meetings, or simply knowing the time elsewhere.
Available City Time Zones
| City | Time Zone | UTC offset (winter) |
|---|---|---|
| Rome | CET | UTC+1 |
| London | GMT | UTC+0 |
| New York | EST | UTC-5 |
| Tokyo | JST | UTC+9 |
| Sydney | AEDT | UTC+11 |
| Dubai | GST | UTC+4 |
| Mumbai | IST | UTC+5:30 |
Daylight Saving Time
Many countries observe daylight saving time (DST), which shifts the clock forward by one hour in spring and back in fall. Not all countries use DST -- Japan and Dubai, for example, do not.
How to Calculate the Difference
The formula is simple: Difference = UTC offset City 2 - UTC offset City 1.
If positive, City 2 is ahead (later). If negative, it is behind (earlier).
Tips for International Calls
- New York to London: 5 hours difference
- New York to Tokyo: 14 hours difference
- London to Sydney: 11 hours difference
The best window for a business call is generally between 9:00 AM and 12:00 PM EST, which overlaps reasonable hours in most European time zones.