Time Zone Converter

Earth is divided into roughly 38 time zones — not 24 — because some regions use 30- or 45-minute offsets (India is UTC+5:30; Nepal is UTC+5:45). Some countries span a single zone for political reasons even when geography would suggest several (China runs on UTC+8 from Shanghai to the western border 3,000 km away).

Daylight saving time adds another layer. The US shifts on the second Sunday of March and first Sunday of November. Europe uses the last Sundays of March and October. The southern hemisphere reverses the direction. Many countries (most of Asia, Africa, and South America) don't observe DST at all. The IANA time zone database (tzdata) tracks every historical and current rule for every region — it's updated multiple times a year as countries change their minds.

When scheduling a recurring meeting across regions, anchor the meeting in one specific time zone (usually the host's) and let attendees see it converted to their local time. This avoids the classic bug where a 9 AM PT meeting becomes 8 AM PT for half the year because someone scheduled it as a fixed UTC offset that didn't follow DST.

For global teams, look for the 'DST overlap window' — the 1–3 weeks in March and November when US and European DST transitions don't align, creating temporary 1-hour shifts in your usual meeting times. Mark these on the team calendar in advance.

When sending an external invite (sales calls, customer meetings), always state the time in the recipient's zone, not yours. 'Tuesday 3 PM ET' is ambiguous; '3 PM Eastern Time / 12 PM Pacific / 8 PM London / 9 PM Berlin' is unambiguous and respectful.

Servers and most APIs return UTC (Coordinated Universal Time, formerly GMT). UTC has no DST and never shifts. When debugging an incident, convert timestamps to your local zone only at the display layer — keep the underlying values in UTC for math and storage.

Common gotchas: ISO 8601 timestamps with a 'Z' suffix (e.g., 2026-05-11T14:30:00Z) are UTC. A timestamp with no zone marker is ambiguous and should be treated with suspicion. Offsets like '+05:30' or '-08:00' are explicit but don't tell you whether DST applies — only the IANA zone name (America/Los_Angeles, Europe/Berlin) carries that rule.

Aviation uses UTC (called Zulu time) for all flight plans, weather reports, and air-traffic control communications. A pilot departing JFK at 14:00 local and arriving at LHR at 02:00 local the next day records both times in UTC to avoid ambiguity. METAR and TAF weather codes are always UTC.

Maritime navigation similarly logs ship positions and radio transmissions in UTC. The international date line at roughly 180° longitude separates calendar days for vessels crossing the Pacific.

The International Space Station runs on UTC internally, though astronauts see sunrise and sunset 16 times per day. Mission control centers in Houston and Moscow coordinate on UTC to avoid shift confusion. Even Mars missions use a 'mission time' based on UTC for consistency across international teams.