send an autoemail as soon as the date in a table changes to system date
I don't know what you mean by this, I don't know what you mean by "date in a table changes to system date".
do you mean an html table or a table in a database? In any case, you could just have some kind of function that "listens" for the change in the table, and as soon as it does, you can either just call a .php page and email to someone using the mail() function OR you can use AJAX to do this with out a page refresh...
so basically you need AJAX and php or some other server script. (well technically you don't need ajax).
most components in html have an "onchange" event handler. but if you want to catch a change in the database, thats a different story. you would have to have some script to keep checking that table for an update, I would think anyways.