The International Date Line: Why Does Travel Cross Dates?
When crossing the Pacific, the calendar may jump forward or back by a day. Learn about this imaginary date boundary.
A Line That Helps Distinguish Dates
The International Date Line roughly follows the 180° meridian across the Pacific Ocean, but it detours around certain countries and islands so that local communities use a consistent date.
Usually, when crossing westward, the calendar date advances by one day; when crossing eastward, the date goes back one day. This does not mean time flows backward—only that the date label changes.
Tips for Travel and Meetings
A trans-Pacific flight may appear to arrive earlier than it departs on the calendar, or skip a day during the trip. Rely on the local date and time shown on the flight itinerary.
When scheduling trans-Pacific meetings, write out the day of the week and date for each city to avoid “tomorrow” meaning different things to different participants.
Put it into practice
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