How to Read UTC Offsets
How to read notation like UTC+9 and UTC−5:30 accurately and quickly calculate the time difference between two cities.
Reading offset notation
A UTC offset shows how far ahead of or behind the reference time (UTC) a place is. A ‘+’ means an earlier time to the east, and a ‘−’ means a later time to the west.
- UTC+9: Seoul and Tokyo (9 hours ahead of the reference time)
- UTC±0: London (winter) and Iceland
- UTC−5: New York (winter)
Calculating the time difference between two cities
Subtract one city's offset from the other's to get the time difference. The difference between Seoul (+9) and New York (−5) is 9 − (−5) = 14 hours. Seoul is 14 hours ahead of New York.
30- and 45-minute offsets
Some regions aren't on the hour. India is UTC+5:30 and Nepal is UTC+5:45, adding minutes to the offset. Even in these cases, the time difference is calculated from the difference in offsets.
The offset shown on a world clock card is the value for ‘this very moment’, with daylight saving time already applied.