How to group columns for a Reporting Services Matrix?

I want to display data in a reporting services matrix. It is an access peak matrix, in a way that days are rows, and hours are columns. My procedure returns data like this:

Day / Hour / Peak
2010-05-01 00:00:00.000 2010-05-01 00:00:00 0
2010-05-01 00:00:00.000 2010-05-01 01:00:00 0
2010-05-01 00:00:00.000 2010-05-01 02:00:00 0
2010-05-01 00:00:00.000 2010-05-01 03:00:00 0
2010-05-01 00:00:00.000 2010-05-01 04:00:00 0
2010-05-01 00:00:00.000 2010-05-01 05:00:00 0
2010-05-01 00:00:00.000 2010-05-01 06:00:00 0
2010-05-01 00:00:00.000 2010-05-01 07:00:00 0
2010-05-01 00:00:00.000 2010-05-01 08:00:00 0
2010-05-01 00:00:00.000 2010-05-01 09:00:00 0
2010-05-01 00:00:00.000 2010-05-01 10:00:00 0
2010-05-01 00:00:00.000 2010-05-01 11:00:00 0
2010-05-01 00:00:00.000 2010-05-01 12:00:00 0
2010-05-01 00:00:00.000 2010-05-01 13:00:00 0
2010-05-01 00:00:00.000 2010-05-01 14:00:00 0
2010-05-01 00:00:00.000 2010-05-01 15:00:00 0
2010-05-01 00:00:00.000 2010-05-01 16:00:00 0
2010-05-01 00:00:00.000 2010-05-01 17:00:00 0
2010-05-01 00:00:00.000 2010-05-01 18:00:00 0
2010-05-01 00:00:00.000 2010-05-01 19:00:00 0
2010-05-01 00:00:00.000 2010-05-01 20:00:00 0
2010-05-01 00:00:00.000 2010-05-01 21:00:00 0
2010-05-01 00:00:00.000 2010-05-01 22:00:00 0
2010-05-01 00:00:00.000 2010-05-01 23:00:00 0
2010-05-02 00:00:00.000 2010-05-02 00:00:00 0
2010-05-02 00:00:00.000 2010-05-02 01:00:00 0
2010-05-02 00:00:00.000 2010-05-02 02:00:00 0
2010-05-02 00:00:00.000 2010-05-02 03:00:00 0
2010-05-02 00:00:00.000 2010-05-02 04:00:00 0
2010-05-02 00:00:00.000 2010-05-02 05:00:00 0
2010-05-02 00:00:00.000 2010-05-02 06:00:00 0
2010-05-02 00:00:00.000 2010-05-02 07:00:00 0
2010-05-02 00:00:00.000 2010-05-02 08:00:00 0
2010-05-02 00:00:00.000 2010-05-02 09:00:00 0
2010-05-02 00:00:00.000 2010-05-02 10:00:00 0
2010-05-02 00:00:00.000 2010-05-02 11:00:00 0
20开发者_StackOverflow社区10-05-02 00:00:00.000 2010-05-02 12:00:00 0
2010-05-02 00:00:00.000 2010-05-02 13:00:00 0
2010-05-02 00:00:00.000 2010-05-02 14:00:00 0
2010-05-02 00:00:00.000 2010-05-02 15:00:00 0
2010-05-02 00:00:00.000 2010-05-02 16:00:00 0
2010-05-02 00:00:00.000 2010-05-02 17:00:00 0
2010-05-02 00:00:00.000 2010-05-02 18:00:00 0
2010-05-02 00:00:00.000 2010-05-02 19:00:00 0
2010-05-02 00:00:00.000 2010-05-02 20:00:00 0
2010-05-02 00:00:00.000 2010-05-02 21:00:00 0
2010-05-02 00:00:00.000 2010-05-02 22:00:00 0
2010-05-02 00:00:00.000 2010-05-02 23:00:00 0
...

My row field in reporting services is the day, column is hour, detail is peak. But when I render the result, it repeats the hour columns for each row.

How to group all 1AM, all 2AM, and so on, given this dataset?

The problem with the procedure result was that time was 1AM, 2AM, etc, but the date part is different for each date.

I just ignored the date part and everything is fine and grouped together.