John Dee, an advisor to Queen Elizabeth I, proposed a calendar differing from the Gregorian calendar only in that the placing of the leap years is different. In the Dee calendar, a year is a leap year if (and only if) the year number, when divided by 33, yields a non-zero remainder which is a multiple of 4. This provides a more uniform distribution of leap years. because in the Gregorian calendar, three times in a 400-year cycle there is an eight-year interval between leap years, while in the Dee calendar, there are never intervals between leap years other than four or five years.

The calendar corrected the Julian calendar by 11 days rather than 10 days as the Gregorian calendar did, so causing the March equinox to occur normally on March 21 rather than having March 21 as the latest possible date. This causes the Dee calendar to normally run one day ahead of the Gregorian calendar. The Dee-Cecil calendar has this one-day difference removed.

Comparison with Gregorian yearEdit

The length of 13,200 Gregorian years is 4,821,201 days. This is one day longer than 13,200 Dee years (4,821,200 days). No shorter cycle can be found that is an exact number of leap-year cycles in both systems. Thus the average length of the Dee year is 1/13200 day shorter than the average length of the Gregorian year.

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