The International Date Line was a line of 180 degrees longitude that marked the change of a day on Earth. It was found in the Pacific Ocean. (PROSE: Chasing the Dawn)
The Eleventh Doctor once went to great trouble to hang a hammock from his TARDIS just on the cusp of the International Date Line. He was relaxing here with a good book when he encountered Amelia Earhart. (PROSE: Chasing the Dawn)