I have in cell p4 the date:
2014-01-01
(obtained via formula (=(((O5/1000/60)/60)/24)+DATE(1970,1,1))
)
I have in cell b5 the date:
2014-0
Perhaps there is a more appropriate comparison format, when you have dates in the format YYYY-MM-DD I think this one will work).
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))