How Time Zones Work
The Earth is divided into 24 primary time zones, each roughly 15 degrees of longitude wide (360° ÷ 24 = 15°). Each zone is offset from Coordinated Universal Time (UTC), the world's primary time standard. UTC+0 covers the prime meridian, while UTC+14 and UTC-12 mark the extremes.
In practice, political and geographic factors cause many countries to adopt non-standard offsets. For example, India uses UTC+5:30 (a 30-minute offset), and some South Asian regions use UTC+5:45. China spans five natural time zones but uses a single UTC+8 offset for national unity.
The IANA (Internet Assigned Numbers Authority) Time Zone Database — also known as the "Olson database" — is the authoritative source for time zone rules, tracking all historical and current DST transitions, offset changes, and zone identifiers like "America/New_York" or "Asia/Karachi".