02-13-2009, 08:01 AM
freeradical wrote:
[quote=Bo]
...and my birthday!
Which means (since it is not a leap year) there's another Fri. 13th next month and a third one in November. I believe that is the most possible in any given year.
Hmm - a number theory kind of problem. How would you go about proving that?
I think it's something along the lines of...there are 14 possible "configurations" for a year since a leap year can start on any day of the week or a non-leap year can start on any day of the week. For a year starting on x day of the week the Friday 13ths will be on xxx/xxx/xxx
Non-leap years:
Sun- Jan/Oct
Mon- Apr/Jul
Tue-Sep/Dec
Wed-Jun
Thu-Feb/Mar/Nov (what we have this year)
Fri-Aug
Sat-May
Leap years:
Sun- Jan/Apr/Jul (the only other config of three in a year)
Mon- Sep/Dec
Tue-Jun
Wed-Mar/Nov
Thu-Feb/Aug
Fri-May
Sat-Oct
Ooop...gotta go. Just got older!