Time Zone Calculator

Local Date & Time

Enter the time in the source time zone below.

Source Time Zone

Destination Time Zone

Empty

Tip: Use UTC for universal coordination or to build schedules across teams.

Time Zone Calculator – Quick Cheat Sheet

Inputs: Local Date & Time (HTML datetime-local), Source TZ, and Destination TZ (IANA identifiers like America/Chicago, UTC, Europe/London).
Conversion is done using PHP’s calendar+zone database (Olson/IANA). DST rules are applied for the selected date.
Offsets show as UTC±HH:MM (abbr) (e.g., UTC−05:00 (CDT)); the difference reflects DST at that moment.
Day change indicates whether the destination date differs (common on long east/west jumps).
Validation: Time zones must be valid IANA identifiers; date/time must be YYYY-MM-DDTHH:MM.
Tip: Use UTC as a bridge when coordinating multi-region meetings.

Edge cases & notes

DST gaps/overlaps: Some local times don’t exist (spring-forward) or occur twice (fall-back). PHP normalizes these.
Half-hour / 45-minute offsets (e.g., India +5:30) are supported; the difference can be fractional (e.g., +5.5h).
IANA vs city names: Use canonical IDs (e.g., America/Phoenix) rather than generic terms (e.g., “MST”).