The Pax calendar was invented by James A. Colligan, SJ in 1930 as a perennializing reform of the annualized Gregorian calendar. Design 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: 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. Jan 04 1931 Jan 03 1932 1937 1943 Jan 02 leap 1938 1944 1949 1955 Jan 01 1928 1933 1939 leap 1950 1956 1961 1967 Dec 31 leap 1934 1940 1945 1951 leap 1962 1968 1973 1979 Dec 30 1929 1935 leap 1946 1952 1957 1963 leap 1974 1980 1985 Dec 29 1930 1936 1941 1947 leap 1958 1964 1969 1975 leap 1986 Dec 28 leap 1942 1948 1953 1959 leap 1970 1976 1981 1987 Dec 27 leap 1954 1960 1965 1971 leap 1982 1988 Dec 26 leap 1966 1972 1977 1983 leap