In leap years, a one-week month called Pax would be inserted after Columbus.
Duncan Steel mentions the Pax Calendar proposal:[2] As a matter of fact, this leap-week idea is not a new one.
Places marked "leap" means that there was no Pax year in the sequence which corresponded to that Gregorian date.
The next table shows what happens around a typical turn of the century and also the full range (18 Dec to 6 Jan) of 19 days that the Pax Calendar New Year Day varies against the Gregorian calendar.
Colligan published multiple alternative methods of organising the months, including three 12-month plans in addition to the 13-month plan, and in a follow-up work focused on two possible 12-month calendars, in which Pax would be between September and October.