Abstract: A binary date format, hereafter referred to as "packed binary", is used and comprises a 2-byte data field. The first two bits of the data field are utilized as identifiers to enable the packed binary format to be identified. The remaining bits are employed as a binary value year indication. A date conversion procedure employs the packed binary format and is called when a program reaches a date field that is to be processed. The date conversion procedure initially examines the date field to determine whether its format is zone decimal, packed decimal or packed binary. If the date field data format is either zone decimal or packed decimal, the date values are converted to packed decimal and the required arithmetic procedure is performed, using the packed binary format date value. Once the calculation is complete, the procedure determines whether a "year 2000" switch is set--indicating that all results are to be returned to the program in packed binary format.