have a cron job run at the time specified. just have a script to do the emailing. the cron job can call php compiled standalone ('/usr/local/bin/php /path/to/script/script.php' for example) or can call the scrip through lynx ('lynx -source "http://yoursite.com/script.php"')
in /etc/crontab add:
01 0 * /usr/local/bin/php /path/to/script/script.php
check the cron syntax tho
