Question

why is international date line not straight?

Answer 1

Tt is not straight as to accommodate same country in same date zone .
Or
Deeply
The International Date line is totally imaginary and political. It was set for the convenience for the countries it passes around, hence the crookedness. It roughly follows the 180 degree longitude line. That line is opposite the politically set 0 degree longitude or prime meridian in Greenwich, UK.

Hope this is help ful

Answer 2

To avoid the confusion of having different dates within the same country, the IDL goes zig-zag at the Bering Strait between Siberia and Alaska and at Fiji, Tonga, New Zealand and some other islands.
Hope it helped.
https://www.youtube.com/c/RyfernzOfficial