The formula for calculating the angle of the event (the number of degrees that need to be subtracted from the ecliptic longitude of the significator of the marriage in order to obtain the value of the MC in the local chart) is as follows:
SA = [DS + VS/24 - (DR + VRp/24) + VD] x 4.9281’
where US is the angle of the event,
DS - date of marriage, regardless of the year (number of the day in the year),
Sun - time of the event (we take everything in Greenwich Mean Time),
DR - date of birth, regardless of the year,
RTp - approximate time of birth,
VD - the number of leap days that have passed in the current 12-year period to the time of the event (since every year the MS in profection returns to the natal position),
4.9281' is the speed of MS movement in the 12-year profection.