The International Date Line: Where Today Becomes Tomorrow
The International Date Line
The International Date Line (IDL) is an imaginary line on the surface of the Earth roughly following the 180° meridian, where the date changes by one day when crossing it.
How It Works
- Traveling west across the IDL: advance one day (Monday becomes Tuesday)
- Traveling east across the IDL: go back one day (Tuesday becomes Monday)
Why It's Not Straight
The IDL zigzags to avoid splitting countries or island groups into two different calendar days. Notable deviations include:
- Russia (to keep all of eastern Russia on the same date)
- Kiribati (moved the line east in 1995 to be all on the same date)
- Samoa (switched sides in 2011)
Practical Impact
When scheduling meetings between cities on opposite sides of the IDL (e.g., Tokyo and Los Angeles), be extra careful with dates. MeetZone handles this automatically, showing both the time and the date difference.