Workflow trigger date

Workflow trigger date

Workflow automation where the trigger date is set and the trigger is 20 days before, work fine if it is in the same month, if the date 20days ahead is the 10th of next month they do not work, has anyone experienced this and if so is there a work around.

I have tested it repeatedly and it will work up to the end of the month, but not in to the following month, rule is set for yearly, have tried monthly and still not working.