How To Cast A Varchar Column To DateTime

Below is my query.Its working great if i remove ,Cast(C.ClassTime as time) as StartDate.But when i use this i get an error as The conversion of a varchar data type to a datetime data type resulted in an out-of-range value My ClassName is a varchar.Whose definition i cant change to DateTime now.But i want to cast it to DateTime.

Code:
Select C.ClassID as Appointment_Id,C.ClassName as Appoitment_Descr,Cast(C.ClassTime as time) as StartDate,C.EndClassTime as EndDate, 'Class' as Type
From Dojo D inner join DojoClass C on D.SchoolID = C.DojoSchoolID
Where D.SchoolID = @DojoID
and C.Days like'%' + @Days + '%'
Union
Select E.DojoEventID as Appointment_Id,E.EventName as Appoitment_Descr , E.EventStartDate as StartDate , E.EventEndDate as EndDate,'Event' as Type
From Dojo D inner join DojoEvent E on E.DojoID = D.SchoolID
Where D.SchoolID = @DojoID and @Date
Between E.EventStartDate and E.EventEndDate

how can i cast it correctly?