When an expiration date is specified when writing a data set, the volume’s expiration date is recorded in the TCDB Volume Expiration Date field. If an expiration date pre-exists for the volume, the later date becomes the new expiration date. If the pre-existing date is later than the new date, the pre-existing date is retained. However, if special “never expire” dates 99365 or 99366 are involved, these special dates take precedence. Special “never expire” dates appear in ISO format as 1999/12/31 for 99365, and 1999/12/32 or 1999/13/01 for 99366.