The only thing I can advice you is this:
- Learn PHP
- Learn SQL
- Write a script wich takes out the joined dates from the database (using a while(list) or so ), and using this little code for transforming the dates to MKtime
Code:
$time = strtotime($time);
and then in the while loop you put the date back in.
It seems simple when I write it down but isn't that simple for doing it right

(I know that because I wrote a similar script wich had to do the same thing too, but for other purposes)