I have a Google Drive spreadsheet where I would like to compute occurrences of date ranges. As you can see in my sheet, there is a column date_utc+1 which contains almost random date data.

https://docs.google.com/spreadsheet/ccc?key=0AhqMXeYxWMD_dGRkVGRqbkR3c05mWUdhYkJWcFo2Mmc

What I would like to do is 1) put the date values into bins of 6 hours each, i.e. 12/5/2012 23:57:04 until 12/6/2012 0:03:17 would be in the first bin, 12/6/2012 11:20:53 until 12/6/2012 17:17:07 in the second bin, and so forth. Then, I would like to count the occurrence of those bins, such as

bin_from            bin_to                freq
-----------------------------------------------
12/5/2012 23:57:04  12/6/2012 0:03:17     2
12/6/2012 11:20:53  12/6/2012 17:17:07    19
...                 ...                   ...

Hope it is clear what I mean. Partial hints are very welcome as well since I am pretty new to spreadsheeting.