  The dominant part in the mental calculation of the day of the week for any
given date is to determine the year share, that is, the contribution of the
two-digit year part of the date. This paper describes a number of year share
computation methods, some well-known and some new. The "Parity Minus 3" method,
in particular, is a new alternative to the popular "Odd+11" method. The paper
categorizes the methods of year share computation, and presents simpler proofs
of their correctness than usually provided.
  Keywords and phrases: day of the week, calendar algorithms, doomsday method,
first Sunday algorithm, mental arithmetic, year share
