# Pax Calendar

The Pax calendar was invented by James A. Colligan, SJ in 1930, as a perennializing reform of the annualized Gregorian calendar.

## Design

Months of the Pax calendar :
| No. | Name | Days |
| 01 | January | 28 |
| 02 | February | 28 |
| 03 | March | 28 |
| 04 | April | 28 |
| 05 | May | 28 |
| 06 | June | 28 |
| 07 | July | 28 |
| 08 | August | 28 |
| 09 | September | 28 |
| 10 | October | 28 |
| 11 | November | 28 |
| 12 | Columbus | 28 |
| 13 | Pax (leap week) | 7 |
| 13/14 | December | 28 |
The common year is divided into 13 months of 28 days each, whose names are the same as in the Gregorian calendar, except that a month called Columbus occurs between November and December. The first day of every week, month and year would be Sunday.
Unlike other perennial calendar reform proposals, such as the International Fixed Calendar and the World Calendar, it preserves the 7-day week by periodically intercalating an extra seven days to a common year of 52 weeks (364 days). In leap years, a one-week month called Pax would be inserted after Columbus.
To get the same mean year as the Gregorian Calendar this leap week is added to 71 of the 400 years in the cycle. The years with leap week are years whose last two digits are a number that is divisible by six (including 00) or 99: however, if a year number ending in 00 is divisible by 400, then Pax is cancelled.
Duncan Steel mentions the Pax Calendar proposal:
   As a matter of fact, this leap-week idea is not a new one. and such calendars have been suggested from time to time. ... In 1930, there was another leap-week calendar proposal put forward, this time by a Jesuit, James A. Colligan, but once more the Easter question scuppered it within the Catholic Church.

## New Year's Day

Unlike the International Fixed Calendar, the Pax calendar has a new year day that differs from the Gregorian New Year's Day. This is a necessary consequence of it intercalating a week rather than a day.
The following tables compare the Gregorian dates (left column) of New Year's Day in the Pax Calendar for various years. Dates in December occur in the preceding Gregorian year. Dates in bold are Sundays. The Pax years run sequentially down each column (from second-left to right), and a new column is begun when the year would need to go further up the column. 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.

## Alternative proposals by Colligan

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. He also provided two alternatives to the leap week plan, either extending one or two Mondays per year to 48 hours or making Pax a month of 28 or 21 days to be added 18 times in 400 years.

## Sources and references

* Lance Latham (1998). Standard C Date/Time Library: programming the world's calendars and clocks. CMP Books. p. 471. ISBN 0-87930-496-0.
* ↑ James A. Colligan (1930). "Original proposal for the Pax Calendar". Rick McCarty.
* ↑ Duncan Steel (2000). Marking Time: The Epic Quest to Invent the Perfect Calendar. John Wiley & Sons, Inc. p. 288, 422. ISBN 0-471-29827-1.
* ↑ Colligan, James (1933). An unchangeable calendar without blank days and with only two days of the present calendar changed. University of San Francisco.