date of a first date time format is converted to any date of a second date time format after a transformation to a temporal reference or epoch date the conversion method can be embedded into any code space to enable full date time conversion abilities the real time conversion of the conversion method requires no conversion tables and no post processing manipulation thus eliminating the need for individual programmers to re create the same date cross reference tables or post processing algorithms the conversion method supports conversion between any two date time formats including the various existing gregorian conventions application_number US 12999408 A description the description and claims herein are directed to a method and apparatus to perform date time conversions and complex date time calculations between dates of different calendaring systems a date time of a first format is converted to any other date time of another format after a transformation to a temporal reference or epoch date referring to fig1 a computer system 100 is one suitable implementation of the apparatus and method described herein computer system 100 is an ibm system i computer system however those skilled in the art will appreciate that the methods and apparatus described herein apply equally to any computer system regardless of whether the computer system is a complicated multi user computing apparatus a single user workstation or an embedded control system as shown in fig1 computer system 100 comprises one or more processors 110 a main memory 120 a mass storage interface 130 a display interface 140 and a network interface 150 these system managers are interconnected through the use of a system bus 160 mass storage interface 130 is used to connect mass storage.