Timezone Converter

Every location on Earth is assigned a time zone that determines its offset from Coordinated Universal Time (UTC). Most offsets are whole hours, but some regions use 30-minute or 45-minute offsets — India is UTC+5:30, Nepal is UTC+5:45, and parts of Australia use UTC+9:30. UTC itself has no offset and does not observe daylight saving time, making it the universal reference point.

Time zones are more complex than simple fixed offsets. Many regions observe Daylight Saving Time (DST), shifting clocks forward in spring and back in autumn. The exact transition dates vary by country and change over time by government policy. The IANA Time Zone Database (also called the Olson database) is the authoritative source for time zone rules and is used by Linux, macOS, most programming languages, and standards bodies. Named time zones like 'America/New_York' or 'Europe/London' are preferred over numeric offsets because they correctly handle DST transitions.

The golden rule for handling time in software: store all timestamps in UTC, apply the user's time zone only at the presentation layer. Storing local times without explicit offset information is a common source of bugs — the same local time string can represent two different UTC instants when a DST transition occurs. Prefer ISO 8601 format with explicit UTC offset or the Z suffix when exchanging timestamps between systems.