setting 'default selected' value for dropdown

Hello guys,
                     I am new to asp.net I am not trying to achieve anythign fancy but just trying to set default selected value for one of the dropdown that I am using.  for that I am doing Items>selected= true for whatever item I want selected when i load the page. In my case, it is a month dropdows and I am selecting date 14 as selected default value out of all 30 values but somehow, out of the blue .NEt decides to show me 29 instead of 14. I am not sure if there  is some another setting that is overwritting this value.
 
Any ideas?
 
...