error while assigning a position to Org Unit

hello all,

i have created a new organization called(it wing through PO10) with valid strat and end date as 01.01.1950 to 31.12.9999

now in relationships , iam trying to add a position (ID = 20000023 , with valid start and end date  as 01.04.1950 to 31.12.9999)

when iam assigining this position getting the folliwing error shown in screen shot,

why does this error occurs, iam not allowed to assign a position which has a valid start date later than the valid start date of the Org Unit...

please clarify on this...