Abstract: A program product performs date and time services for a calling program. The program product accepts multiple date and time inputs, multiple date and time input and output formats, and multiple function requests. A windowing function is performed to determine a century value for a date that lacks a century designator. Gregorian, Julian, ADABAS D, ADABAS T, EIBDATE, and other formats are supported. Formats may also be parameterized for individual functions allowing a calling program to select multiple and diverse formats for a sequence of called functions. Version checking and version tracking are also supported to insure the calling program interfaces with a version of the program product having an expected functionality. A method provides the functionality of the program product, receiving calls from a calling program. Another method embodies a calling program performing date and time operations by invoking a date and time services program.