Research found no evidence to support myth that women’s cognitive abilities change across menstrual cycle. Given physiological changes that occur across menstrual cycle, the changes to the brain are either small enough that they don't influence performance or women compensate for these changes.

[u/mvea]

https://www.scimex.org/newsfeed/womens-menstrual-cycles-dont-change-the-way-our-brains-perform

[u/yogalalala]

Taking the day off isn't really practical if your "bad days" are 5 or more days a month.