My brother's birthday is on November 22. Once every 7 years, on average, his birthday falls on Thanksgiving. I was curious about when exactly that would occur in the future so I did something like this in the bash shell on a GNU system: for year in $(seq 2008 2060) ; do date -d 11/22/$year | grep Thu ; done And if you try it, you'll see what happens -- it fails starting in 2038. It also fails if you go back before 1970. By the way, this method works for any range of years: for year in $(seq 1960 2060) ; do cal 11 $year | egrep -B5 '^18 19 20 21 22' | grep November ; done That is, it shows you every November for the given range of years where the 22nd of the month falls on a Thursday. Thanksgiving wasn't on the fourth Thursday of November until the 1930s -- before that it was on the final Thursday of the month and therefore would always have been on 11/29 instead of on 11/22. Funny what you can do easily with these GNU programs, eh? Mike