Perpetual calendar uses table with 18 columns of seven figures and letters to determine day and date in any past of future year

摘要

The calendar uses a table with 18 columns of six figures in 126 boxes for the hundred years in a century and 25 bissextile years, tables in which the first year in each century is accorded a letter between A and G according to the first Sunday in the year, and a table of the days of the month in columns headed A to G.