How many weekends can you have in a month? This happens once every 823 years and March 2013 is one of them.
October  had 5 Fridays, 5 Saturdays and 5 Sundays all in one month. It happens only once in 823 years
The calendar cycles completely every 28 years.
Any 31 day month will have the first three days of the month repeated 4 times, for a total 3-day series occurrence of 5 for the month.
If the first of the month falls on Friday, the month will be a 5-F-S-S month. Since there are seven 31-day months each year, the 5-F-S-S event will occur 28 times every 28 years. Any given month will have 5-F-S-S 4 times every 28 years, whenever the month begins on Friday.
Is that 6 times every 7 years on the average?
(((your inner voice.com)))