try figuring out in your head if there ane more Friday the 13ths or Tuesday the 13ths.

Obviously dependent upon the time-period selected.

The mental calucation is simplified somewhat by noting that if Tuesday is the 13th of a 31-day month (and 7/12th of the months qualify), then Friday will be the 13th day of the following month. (E.g. in 2002 August 13 is a Tuesday; September 13 is a Friday.)