I'm trying to recreate your problem.
DateTime dt1 =DateTime.ParseExact("19-06-2014 00:01:13", "dd-MM-yyyy HH:mm:ss",null);
DateTime dt2 =DateTime.ParseExact("18-06-2014 23:58:13", "dd-MM-yyyy HH:mm:ss",null);
with above two DateTime objects,
var minutes = (dt1-dt2).TotalMinutes;