With reference to the IDL, the day on Earth starts in the West and ends in the East.
It is one and the same day only at 12 o’clock midnight at the 180° meridian.
For the countries lying to the east of it i.e. the USA, Chile, etc., it is the end of the day while for the countries lying to the west of it i.e. Japan, Australia, etc. it is the start of a new day.
Thus, a new day starts in the Pacific Ocean on Earth.
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