increment/decrement url variable

[BEFOR]

I need to do a nav bar that will increment and decrement for years and for months. The incremented or decremented month or years as a result of the nav link should show in the url variable as date=yyyy-mm-dd

The page starts on a query:

WHERE DATE_FORMAT(event.datestar,'%Y%m') = DATE_FORMAT(CURRENT_DATE(),'%Y%m')

Which works. Also this page sometimes has a url varialble as:

site.php?date=yyyy-mm-dd

In the url and I would like to check on this first if possible.

Do I need to define page variables to do this?

Any help much appreciated.

[batman]

its kinda confusing what your asking, but ill give it a shot... Im not really sure how you would increment a year or month with the CURRENT_DATE(); function, but this is what i would do:
set a date variable, for instance:

$date = $_GET['date'];
if($date = "")
{
$date = CURRENT_DATE(); // MAKE SURE ITS IN YYYY-MM-DD format
}
$sql = mysql_query("your query");

Then provide some kind of text box or something where they can enter the date they want in the YYYY-MM-DD format. Then what it will do is search database for the date they enter but if nothing is entered then it will go with the current date..Im confusing myself now so i best stop. Hope that helps.

P.S. you will have to update your query to search by $date and not CURRENT_DATE(); =D