Timer doesn't wait. Do
/timer 1 86400 .echo -a blah
Does mIRC freeze up for a whole day? Of course not, that says "execute the echo command one day from now" not "wait one day, don't do anything at all, then execute the echo command". Timers are used to schedule an event, not to wait until an event occurs. If you can't understand that then the simple answer is, you can't do this.
