How does the retest date get set for an item?

Suggestion:
Retest is the process of determining the efficacy of the
material after the given shelf life has passed.
Retest Date gets set , when the value in Auto Periodic Retest field in siteitem or in item master is defined as ‘Yes’, then the system will set the value in this field as Cycle Time for period retest entered in the item master.
Shelf life type selected as ‘Retest’/ ‘R’. Users have to enter the Retest days for shelf life.
Note:
QC order retest date needs to entered.