Datepart,Datename DateAdd, DateDiff, Date

DatePart- Returns an integer tat represents the specified datepart of the specified date.
DATEPART (DatePart, Date)

DateName- Returns a character string that represents the specified datepart of the specified date.
DATENAME (DatePart, Date)

DateAdd-Returns a specified date with the specified number interval added to a specified datepart of that date.
DATEADD (DatePart, number, date)

DateDiff-Returns the time between two dates.
DATEDIFF (DatePart, StartDate, EndDate)