Doing that you will need a huge database in the backend with every day of every special day. But it might not work as there are many special days on one day or even one special day might occur on two days.
If you have only one day per date, I would send the date (or the description of the day) to the backend and then return the possible suggestions. I would even enable autocompletion for the description if you don't have any date set.
In the response for the description I would show both, the text and the date in bracets and then add the date to the first input, as soon as the user selects an option.
Kau-Boy
2010-07-12 15:41:51