Unable to enter the COntract end date as blank in spro

Hi Experts ,

I have to set in the schedule condition the contract End date as Blank in spro I have done the changes , but when I try to schedule the action on a contract with blank contract end date the action is not getting scheduled and it seems  there is some issue while setting the blank value , because when I set the date as 31129999 , it is working properly , please suggest .

Thanks ,

Vaibhav