You're welcome, of course. It's probably a good idea to get into the habit of making things as simple as possible --- less code, less variables (if you're not going to use something more than once, that is) equals less server load and a "quicker" website.
AAMOF, since you've got a php [man]echo/man in your HTML, it should probably be just:
<input type="hidden" name="date" value="<?php echo date("Y-m-d H:i:s"); ?>">