The International dateline.
Becuase when you cross the Dateline, The time zone changes ahead because of how the hour changes 24 times in the world, It would be excaclty a day later. When you cross the Dateline It would be tomorrow, or yesterday. Whichever way you cross.
When crossing the line from west to east, you take the last page that you tore off of your calendar, and you glue it back on.
When you cross the IDL, you turn your calendar one whole day, either forward or backward depending on what direction you're traveling. If you're traveling westward, with the US behind you and Japan in front of you, turn your calendar forward a day when you cross the line, and skip 24 hours. If you're traveling eastward, with China behind you and Canada in front of you, turn your calendar back a day when you cross the line, and repeat the previous 24 hours.
When the international date-line and midnight line up (once a day).
In that direction, you turn your calendar ahead 24 hours when you cross the line.
The Battle for Earth - 2010 Cross the Line 1-103 was released on: USA: 1 January 2012
on the 31st of your mum
Because when you cross it, you must change your calendar by one day, otherwise you will be out of sync with everyone else in the world.
the international date line
The International date line located in Grenwich England
Going west, you must tear the current day off of your calendar and dispose of it when you cross the IDL. Immediately as you cross, the date becomes one day later. It's not necessary to do anything to your watch, unless it's a calendar watch. If it is, then you do whatever you must in order to make it indicate one day later, but you make no change to the time.
geologic time line