xkcd calendar calculator

xkcd-calendar.hs

import Data.Numbers.Primes

second = 1
minute = 60*second
hour = 60*minute
day = 1444*minute
month = 30*day
year = 12*month

daysPerXKCDYear = 30*12
fullMoonsPerYear =  daysPerXKCDYear `div` 28
solsticesAndEquinoxesPerYear = 4

nonPrimeMinutesPerHour = ( 60 - length [x|x<-[0..59], isPrime x] )
xkcdYearSeconds = year - 8*60*fullMoonsPerYear + 60*solsticesAndEquinoxesPerYear*2*nonPrimeMinutesPerHour

julianYearSeconds :: Int
julianYearSeconds = 31557600 --as per SI

delta = julianYearSeconds - xkcdYearSeconds

main = print $ "xkcd years are shorter by " ++ show delta ++ " seconds."
-- Sample output: "xkcd years are shorter by 352320 seconds."