1) why does the rotation of earth require people to establish time zones? 2) what is a leap year, and what purpose does it serve? 3) what line on earth's surface marks where the date changes?

1. Since the Earth rotates constantly and is exposed to the sun in different

2. a leap year is february 29th and it appears every 4 years on the gregoriancalendar. it exists to keep seasons where they are in relation to the year.
3. International Date Line IDL

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