Video of final model (see below for development thread) ---- Not quite sure what to call this thing... A machine to instantly calculate the day of the week for any calendar day of any year (e.g. birthdays, etc.) There will be four hand turned knobs to select the century, year, month and date, and the day of the week will then be displayed. The idea is to do it with differentials, and lots of 1:7 gear ratios. Leap years will be accounted for automatically by an