Here is one way to do this.
Put dates in column A. For this example I had dates in cells A2 to A24.
(You can change the location of the dates later, once this is working).
To get the 12 months as headers:
In Cell B1 enter 01-Jan-2010 and format in a suitable date format
In Cell B2 enter the formula =EOMONTH(B1,0) and format in a suitable date format
In Cell C1 enter the formula =B2+1
In Cell C2 enter the formula =EOMONTH(C1,0)
Select cells C1 and C2 and extend the formulas out to column M by dragging or copy and paste.
Cell M2 will now have 31-Dec-2010
Now the formula that does the real work:
In cell B3 enter this formula: =SUMPRODUCT(($A$2:$A$24>=B1)*($A$2:$A$24<=B2))
Note the $ signs
Extend this formula out to Column M
The number of dates falling in each month will now be in row 3, under each date range.