As a female engineer and a feminist, if I were implementing this feature I would have obviously known that periods can last forever. Unfortunately given that Fitbit's engineering team is majority male, some male engineer is probably going to push a fix in response to this article that removes the explicit upper limit on period length while still using an int32 or int64 to represent it instead of using a big integer type as they should to represent periods lasting over 9,223,372,036,854,775,807 days which is possible if you are a really, really hardcore feminist.