By "close a link", do you mean to simply not show it on that certain date? If that's what you mean, try the following:
<?php
$closeDate = "2-14-2007";
/* Date you want the link not to be displayed. Format: Month-Day-Year (2-14-2007) */
if (date('n-j-Y') == $closeDate) {
//do not echo link
}
else {
echo '<a href="link.php">Test Link</a>'; //the link to be echoed
}
?>
Basically what the above does is compare the date you type into the $closeDate variable with the current date of the server. If the dates match, do not display the link. If they don't match, display a link.
Hope this helps.