Abstract: A date formatting system for a computer program to perform date operations where the dates span more than one century. In a first embodiment, a 6-integer file system in CYYDDD format is used, “C” being a variable indicating the century, YY indicating years, and DDD indicating days of the year. A second embodiment utilizes a 7-digit integer data file and is in YYYYDDD format. These two embodiments help avoid problems experienced by computer programs that use 2-digits to identify years.