Abstract: The day-name associated with any date under the Gregorian Calendar is determined by a process which first identifies, from tabulated data correlated to seven day-name categories, the day-name assigned to the first day of a centesimal year. Additional tabulated data correlates the day-name for the first day of a centesimal year to the day-name of the first day of any year within the century following the centesimal year. A third data set correlates the day-name for the first day of any particular year to the day-name for any particular month and number date within the year.