The intuitive answer is 24 — one zone for each hour in the day, each 15° of longitude wide. But Earth's actual number of time zones is 38, because many countries use offsets that fall on the half-hour or even the quarter-hour.
Whole-Hour Zones
Most of the world runs on whole-hour offsets from UTC: UTC−12 through UTC+14. Yes, UTC+14 exists — the Line Islands (part of Kiribati) use it, making them the furthest ahead of any zone on Earth. They share a calendar day with UTC−12 for a brief window each day.
Half-Hour and Quarter-Hour Zones
Several countries use offsets that are not whole hours. The most notable are India (UTC+5:30), Iran (UTC+3:30), Afghanistan (UTC+4:30), Sri Lanka (UTC+5:30), Myanmar (UTC+6:30), and the Marquesas Islands (UTC−9:30). Australia uses a mix — its eastern states are UTC+10 or UTC+11 in summer, while South Australia and the Northern Territory are offset by 30 minutes from them.
Nepal uses UTC+5:45 — a 45-minute offset — making it the only country in the world with a quarter-hour offset relative to UTC. Chatham Islands (New Zealand) uses UTC+12:45 in standard time.
