I’ve gotten a few comments about how special some months are, in particular the months that have 5 Fridays, 5 Saturdays & 5 Sundays in them. The myth is that this only happens once every 823 years. So I guess I wanted to clear this up for you and give you the facts around this myth.
Months like this coming March (2013) fall into this pattern. Since March always has 31 days, and a week is always 7 days, March will include these same 5 days anytime the month begins on a Friday (like next year). Since a week has 7 days, and a standard year consists of 52 weeks plus 1 day, March begins on a Friday an average of once every 7 years (not every 823 years).
Due to leap years, however, March does not begin on a Friday exactly once every 7 years; instead, it follows a 6-5-6-11 pattern. So when March begins on a Friday, that occurs again 6 years later, then 5 years later, then 6 years later, and finally 11 years later, whereupon the cycle repeats. Thus we see patterns of Friday-beginning March in clusters of years like the following: 1996, 2002, 2007, 2013, 2024, 2030, etc.
We’re approaching the end of a cycle and thus the longest gap between occurrences, but that gap is only 11 years, not 8 centuries.