Are you sure this math is correct? Have you accounted for every 4th February having 29 days? This might tend to alter that calculation by pushing days beginning with March 1 in a leap year two days ahead of the immediate previous non-leap year. That is, if March 1 is on a Sunday, it would be on a Monday the following year...but in a leap year it will be on a Tuesday, etc. This means that in a leap year that might have had 5 ea. F,S,S that cycle might be disrupted.