Syntax for a TSQL date time variable
DECLARE @START_DATE DATETIME
DECLARE @END_DATE DATETIME
SET @START_DATE = '09/21/2012 00:00:00'
SET @END_DATE = '09/21/2012 23:59:59'
SELECT * FROM TABLE WHERE POSTINGDATE >= @START_DATE and POSTINGDATE <= @END_DATE
DECLARE @END_DATE DATETIME
SET @START_DATE = '09/21/2012 00:00:00'
SET @END_DATE = '09/21/2012 23:59:59'
SELECT * FROM TABLE WHERE POSTINGDATE >= @START_DATE and POSTINGDATE <= @END_DATE