Calculating Onot

A woman anticipates her menses on certain days based on her previous menstrual pattern. These may include

• yom hachodesh (the day of the month)


• the haflagah (the interval between periods)


• onah beinonit (the thirtieth day)


• veset kavua (a regular period established over at least three cycles)


• veset haguf (specific physical symptoms)

This section deals with the rules for calculating days of anticipated menses (called vesatot, or onot perishah).