Time reference

International Date Line

Why crossing the Pacific can change the calendar date.

International Date Line matters because many everyday scheduling mistakes come from treating time as a fixed label instead of a rule tied to a date, place, and time zone database.

For practical planning, compare the actual event date and use IANA time zone names when possible. Fixed offsets are useful shortcuts, but they can miss daylight saving transitions and local rule changes.

This guide is written for ordinary scheduling, travel, remote work, webinars, and calendar planning. It is not official legal or safety-critical timekeeping advice.

Useful next step

Open the time zone converter when you need to compare an exact date and time. Open the world clock when you only need the current local time.