For something more or less related, check out the calculation of the date of Easter: http://en.wikipedia.org/wiki/Computus http://en.wikipedia.org/wiki/Computus

For something more or less related, check out the calculation of the date of Easter: http://en.wikipedia.org/wiki/Computus http://en.wikipedia.org/wiki/Computus. Some versions, like Gauss' algorithm, also relied heavily on moduli.