UTC Offset Explained: How Time Zones Are Actually Defined
Sunil Kalikayi4/8/20264 min read
How UTC Offsets Work
UTC+0 is the reference (Greenwich, UK). Each hour east adds 1 to the offset: UTC+1 (Central Europe), UTC+5:30 (India), UTC+8 (China, Singapore), UTC+9 (Japan, South Korea). Each hour west subtracts 1: UTC-5 (US East), UTC-8 (US West). Non-integer offsets exist: India UTC+5:30, Nepal UTC+5:45, Iran UTC+3:30.
The International Date Line
At UTC+12/UTC-12 (180° longitude), the date changes — crossing east adds a day, crossing west subtracts a day. Countries near this line choose which side they want: Kiribati chose UTC+14 to stay in the same date as their western neighbors despite geography.
Frequently Asked Questions
Convert with UTC offsets
Use the Time Zone Converter to convert between any UTC offsets.
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