Find How Long Items Open Using Date Columns

I have a sample view with some dates. How would you find the numbers of items open per month. Say between OpenDate and CloseDate I want to find how many were open for January, February,?

Here is a sample table with the data

Code:
CREATE TABLE [dbo].[TestDate](
[ItemTitle] [nvarchar](50) NULL,
[ItemAttachAssignDate] [date] NULL,
[ItemDetachConcludeDate] [date] NULL,
[Status] [nvarchar](50) NULL,
[FullName] [nvarchar](100) NULL,
[OpenDate] [date] NULL,
[CloseDate] [date] NULL
) ON [PRIMARY]
GO

Code:
INSERT INTO [TestDate]([ItemAttachAssignDate], [ItemDetachConcludeDate], [Status], [FullName], [OpenDate], [CloseDate])
VALUES('2013-02-18 00:00:00', '2013-02-19 00:00:00', 'Done', 'Jeff Hunter ', '2013-02-18 00:00:00', '2013-02-19 00:00:00');
INSERT INTO [TestDate]([ItemAttachAssignDate], [ItemDetachConcludeDate], [Status], [FullName], [OpenDate], [CloseDate])
VALUES('2012-10-15 00:00:00', '2013-02-05 00:00:00', 'Done', 'Tommy Johnson', '2013-01-22 00:00:00', '2013-01-28 00:00:00');

[Code] .....