Veset Hachodesh
Veset Hachodesh is an Onat Perishah based on the date of the Hebrew month on which the Re'iyah began and the Onah in which it began
Veset Hachodesh uses the same day of the next Hebrew month and the same Onah, based on the latest source event at that point in history No monthly chain is generated without a new source event The basis for the monthly date is described in Shulchan Aruch, Yoreh De’ah 189:2
When day 30 is missing in the next month, select day 1 of the following month, day 29 of the short month, or omission For example, 30 Nisan maps to 1 Sivan, 29 Iyyar, or omission The current profile defaults to day 1 after the short month; this product choice is not a universal ruling