Range date SQL 2008. If a record is set in the same time in two different rows

Hi guys a quick question: having a date (nvarchar format) like this 2013-02-22 00:00:00.0000000 how can I transform in date? And most important, having a structure like

idRec idContract From To

1 11  2013-02-22 00:00:00.0000000  2013-04-22 00:00:00.0000000

How can I check if the idRec is in two different period? I mean in two different contract in the same time..

Any advice?

Thanks