bogus-october-thing.sh

#!/bin/sh

SPESHUL=0
START=1582 # start of Gregorian
END=2010
RANGE=$(( ${END} - ${START} ))

for YEAR in $( jot - ${START} ${END} ) ; do
  # cal outputs fixed positioned columns, but need to ditch header and blank lines
  FRI=$( cal 10 ${YEAR} | cut -c16,17 | tail +3 | grep -v '^\s*$' | wc -l )
  SAT=$( cal 10 ${YEAR} | cut -c19,20 | tail +3 | grep -v '^\s*$' | wc -l )
  SUN=$( cal 10 ${YEAR} | cut -c1,2   | tail +3 | grep -v '^\s*$' | wc -l )

  # yes, string comparison is cheaper but you have to clean the strings first, meh
  if [ ${FRI} -eq 5 ] && [ ${SAT} -eq 5 ] && [ ${SUN} -eq 5 ] ; then
    SPESHUL=$(( ${SPESHUL} + 1 ))
  fi

done

echo ${SPESHUL} ex ${RANGE}

[lemon@far ~] 0 $ ./bogus-october-thing.sh 
61 ex 428

lots more than 1 ex 823 per Twitter RT everywhere.