For most people who menstruate, they bleed for around 7 days but that’s not the number of days spent in pain, which are typically 1-3 days with varying levels discomfort. Peak discomfort may only be for a few hours when appropriately treated. Flexibility here might include working from home if an option, where you can be under a heat pack and well medicated, up to time off (partial days off here can be important!). People who need to take multiple days off a month for this 1) probably would do it anyway and maybe call it a headache or something else instead, and 2) may need further medical care and attention (that they may be able to receive if they aren’t spending all of their sick time on this one issue).