If you have the CLI build of PHP installed, then cron can do it.
daleco@localhost [/var/home/dalecosp] 21:43
#whereis php
php: /usr/local/bin/php
daleco@localhost [/var/home/dalecosp] 21:44
#crontab -l
30 16 19 8 * /usr/local/bin/php - q /var/home/dalecosp/reminder.php
If you don't, but have lynx, that might be a possibility:
daleco@localhost [/var/home/dalecosp] 21:45
#crontab -l
30 16 13 8 * /usr/local/bin/lynx [url]http://mysite.com/myscript.php[/url]
HTH,