Surely this is the date from the period of service (PPS) row that is being displayed? So it will not appear on any of the people/employee API's.
I can't remember if there is a PPS api lurking? If there is it is probably an internal developer one. In which case you could either hack DP to generate an API interface for the internal API, or write a user-hook onto the employee API to go and do the update of the PPS row.
Of coursse, if it has nothing to do with the PPS record, and you are still stuck with no DP parameter, then the user-hook route may well be your only option.
For historic reference, i remember having this situation at Yorkshire Building Society (Eons ago), when financials went in before HR/Pay. In this scenario (and it pre-dated DP by many years) we ended up hacking the dates as part of the API wrapper script process (ah, those were the days <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> )
_________________________
HCM Aces is for sale! Please contact me if you are interested.
Also
my random musings courtesy of Twitter