I have in cell p4 the date: 2014-01-01 (obtained via formula (=(((O5/1000/60)/60)/24)+DATE(1970,1,1)))
2014-01-01
=(((O5/1000/60)/60)/24)+DATE(1970,1,1))
I have in cell b5 the date: 2014-0
2014-0
You should be safe with chopping the parts up and reassembling them:
=DATE(YEAR(P4),MONTH(P4),DAY(P4))=DATE(YEAR(B5),MONTH(B5),DAY(B5))