* Fix leap year check
Replace `!=` in `(year % 400) != 0` (line 49) with `==`
Justification: Years that are divisible by 100 (centurian == 100) but not by 400 (year % 400 != 0) are skipped and NOT leap year.
* Update parentheses
Correct the parentheses to make clear the precedence of the conditional check
* Update other/doomsday.py
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>
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Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>