Vivenza
Vivenza is the day of birth counted as the first day lived. In the classic biorhythm method, one is added to the days elapsed since birth, because the day you are born is already a day of life. Without that plus one, all three positions in the cycles would be shifted by a day.
It is a detail that sets the classic method apart from many online calculators: simply subtracting two dates gives the days elapsed, not the days lived. The first day of life is day one of all three cycles, that is a triple critical day, and the count runs on from there.
In the couple calculation vivenza does not apply: there you compare the distances between two dates, and the extra day would cancel itself out.
For someone born on 15 June 1990: 36 full years make 13,140 days, plus 9 leap days and 79 days from the last birthday to 2 September 2026, plus 1 for vivenza. 13,229 days in all, from which the three cycle positions follow.