The International Date Line is an imaginary line of longitude at 180 degrees that runs from the North Pole to the South Pole. It marks the boundary between one day and the next.

When you cross the International Date Line from east to west, you gain a day. This is because you are moving from a later time zone to an earlier time zone.

When you cross the International Date Line from west to east, you lose a day. This is because you are moving from an earlier time zone to a later time zone.

When it is January 1st on one side of the International Date Line, it is December 31st on the other side.

When it is December 31st on one side of the International Date Line, it is January 1st on the other side.

The longest day of the year on one side of the International Date Line is June 21st.

The shortest day of the year on one side of the International Date Line is December 21st.

The time difference between two places on opposite sides of the International Date Line is 24 hours.

Kiritimati is the name of the island that is located on both sides of the International Date Line.

Kiribati is the name of the country that is located on both sides of the International Date Line.

Pago Pago is the name of the city that is located on both sides of the International Date Line.

Pago Pago International Airport is the name of the airport that is located on both sides of the International Date Line.

UTC+12 is the name of the time zone that is located on both sides of the International Date Line.

The 180th meridian is the name of the meridian that is located on both sides of the International Date Line.

The Treaty of Washington is the name of the treaty that established the International Date Line.