I recently coded for a similar problem, it was a calendar that printed dates of events. Mine used a file to store events because Mysql was not available, however, Mysql would be better and it wouldn't be much to change it over. I will post the script tonight when I can get to my files! My script was based on this:
http://keithdevens.com/software/php_calendar/
so you could use this aswell, it is very similar to mine. You will still need to do some code to get when you are not available from the mysql. By the by if you follow this method your table should be something like:
id, timestamp (php or mysql), title, description
This could then easily store when you are not available.