Check difference between results not listed and identify which day is the date
Check out my answer to the following question on StackOverflow

https://stackoverflow.com/questions/3093924/select-all-months-within-given-date-span-including-the-ones-with-0-values/3111441#3111441

You could easily apply this method to your problem, and return data for all the days between a range, including those with no data content.

Dave