repeat 31 day every 1 month

do this repeat type has a bug?and,if this is’nt a bug,why? thank you.

when you specify “repeat every n-th day of month” and if specified number is greater than number of days in month, the event is created on the next month (default behavior of JS dates). So this is not considered as a bug.

However, probably you’ve needed it to “repeat on the last day of each month”. If so, unfortunately this pattern is not supported, and there is no easy way to implement it