You are taking the wrong approach. The database is storing the dates in it's own format. If you want to use this one, you need to parse it as DateTime to store in the database and use the formatter to display it this way.
You have all the formatting options here:
http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx[
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According to it you need something like this:
"dd-MMM-yy:hh:mm:ss". And don't forget to use the proper locale to have the month name as you need.
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