Why does the IDL run zig zag through the earth surface?

Question

Why does the IDL run zig zag through the earth surface?

Answer 1

Because every country is free to assign their time zone as they wish. It's not an internationally agreed-upon line, it's just the one that indicates how each country that is affected by it has chosen to make their time zone. The same is true for all time zone lines.

Answer 2

so you don't get that awkward situation where half a country is on Sunday and the other half is on Monday because that creates all kinds of complications