What to use to send an email atomatically at certain time of day

Hi there,

I am looking to do a bit of testing with codeigniter with sending an automated email to a specific account without me on the system.  So what I would love it to do is say at 1pm every day it kicks off s script to create and send an email.  I know how to create the email part, I am just trying to find out what I should be using to get it to automatically send it at 1pm, can I do this in php or would I have to look at jquery or something else like that?

Thanks,

Doomie