The Complete Guide to Timezone Conversion

Timezones confuse because they are not pure math — they are politics layered on geography, with offsets that change twice a year. Understanding the pieces makes the math reliable.

The anchor: UTC

All timezones are defined by an offset from UTC (Coordinated Universal Time). UTC itself has no offset — it is the reference. "UTC+8" means the local time is always UTC plus eight hours. When computers exchange times, they almost always use UTC.

Offsets vs zone names

An offset (+8:00) is constant; a zone name (Asia/Singapore) is an offset plus DST rules that can shift it. This is why "8am +8:00" is stable but "8am Singapore time" changes across DST transitions in spring and autumn. Use IANA zone names for anything that recurs.

Daylight saving: the source of most bugs

Spring forward, fall back. Most zones shift one hour twice a year — on different dates in different regions (late March in Europe, mid-March in North America, and some zones do not observe DST at all). A schedule fixed by offset is immune; a schedule fixed by "local time" shifts.

Fair global scheduling

Identify the overlap of working hours (8am–6pm) across all zones.
Pick a slot in the overlap — if none exists, rotate who absorbs the bad hour.
State the time in UTC or with explicit zone names for clarity.
Re-check after every DST transition weekend.

Unix time: the unambiguous format

A Unix timestamp is the same instant for every human on Earth — no zone, no offset, no DST. For logs, event payloads and stored times, it is the safe choice. Convert it to local time only for display.

The Time Converter uses the browser's zone database, so DST is applied correctly for the specific date you ask about.

Why does my meeting time shift by an hour in April?

Daylight saving time. The offset for that zone changed, so the local time moved by one hour. Re-check recurring meetings after DST transitions.

Tools for this task