The world on different clocks
When it is 9:00 AM in New York, it is already 3:00 PM in Paris and 11:00 PM in Tokyo. Each region keeps a local time defined as an offset from Coordinated Universal Time (UTC), the world’s reference time kept by atomic clocks. Converting between two places only requires the difference between their offsets, and attention to daylight saving time.
How the conversion works
Time there = time here + (offset there − offset here)
If the result goes past midnight, the date changes: the calculator shows whether the converted time is on the next day or the previous day.
Worked example
You want to call a colleague in Paris at 9:00 AM New York time in winter:
- New York in winter: UTC−5. Paris in winter: UTC+1.
- Difference: +1 − (−5) = 6 hours.
- 9:00 AM + 6 h = 3:00 PM in Paris, the same day.
Common offsets
| Place | Standard time | Daylight saving time |
|---|---|---|
| Honolulu | UTC−10 | none |
| Los Angeles | UTC−8 | UTC−7 |
| Denver | UTC−7 | UTC−6 |
| Phoenix | UTC−7 | none |
| Chicago | UTC−6 | UTC−5 |
| New York | UTC−5 | UTC−4 |
| London | UTC±0 | UTC+1 |
| Paris, Berlin | UTC+1 | UTC+2 |
| India | UTC+5:30 | none |
| Beijing, Singapore | UTC+8 | none |
| Tokyo | UTC+9 | none |
| Sydney | UTC+10 | UTC+11 |
Daylight saving time
Most of the United States and Canada move their clocks forward one hour on the second Sunday in March and back on the first Sunday in November. The European Union changes on the last Sunday in March and the last Sunday in October. Because the dates differ, the gap between New York and London or Paris shrinks by an hour for a few weeks each spring and fall. Arizona (outside the Navajo Nation), Hawaii and most of Asia do not use daylight saving time. In the Southern Hemisphere, places like Sydney and Auckland observe it from October to April.
Choose the offset that applies on the date you care about: the list shows which cities use each offset in winter and in summer.
Unusual offsets
Not every time zone is a whole number of hours from UTC. India is at UTC+5:30, Newfoundland at UTC−3:30 (−2:30 in summer), Nepal at UTC+5:45 and central Australia at UTC+9:30. China spans five geographic time zones but uses a single offset, UTC+8, everywhere.
Tips for scheduling across time zones
- Name the time zone in every invitation, for example “10:00 AM ET”, or use UTC for international teams.
- For recurring meetings, check the weeks when daylight saving time starts and ends on different dates in the two countries.
- Calendar apps convert times automatically when you set the event’s time zone correctly.
- Remember that the date can differ: a Monday morning meeting in Sydney is still Sunday afternoon in California.