You lose a day
The International Date Line separates Day 1 from Day 2 across the globe. Thus, if you are crossing the Internationa Date Line, you may be a day ahead or behind of the place you have travelled from.
It becomes one day earlier.
if you travel east across the international dateline your calendar would be moved back a day.If you traveled west, you would move your calendar a day ahead.Weird, huh?
yup
You go forward one day
Yes. If you travel from west to east across the International Date Line, the date will change to one day earlier.
the international date line
If you are crossing date line from west to east you'll gain one day.
Across the united states
180°
You don't gain a day by traveling West, only by traveling East. You lose a day going West.
If you travel west across the International Dateline, then before you reach your destination and interact with other people who haven't traveled along with you, you need to tear an extra day off of your calendar, and crank your wristwatch ahead to 24 hours later.