Jesper's... Rule Brazil 2012 only - Feb Sun>=22 0:00 0 - ...does seem preferable to using the actual dates; as Jesper notes, it "will give a hint on how the dates behave after 2038." Another possibility is to express the rules as... Rule Brazil 2008 max earlycarnival Feb Sun>=15 0:00 0 - Rule Brazil 2008 max latecarnival Feb Sun>=22 0:00 0 - ...with suitable additions to the "yearistype" script--including, but not limited to, 2-earlycarnival|2-latecarnival) case $1 in 2012|2015|2023|2026|2034|2037) late=1 ;; *) late=0 ;; esac case $2-$late in earlycarnival-0|latecarnival-1) exit 0 ;; *) exit 1 ;; esac ;; Yet another possibility is to cobble up a Carnival calculating executable that can be used by yearistype (instead of hard-coding the years as above). Both this approach and the hard-coded approach merit caution: the yearistype mechanism hasn't been used for real-world stuff in some years. Long term, given the non-repeating nature of Carnival (it's not on a 400-year cycle since it depends on the phase of the moon) it might be best to incorporate the Carnival calculator into localtime; that's a non-trivial endeavor. For purposes of getting something correct and safe out the door now, I'd go with Jesper's approach. --ado