24 hours timer not working

Question

Hi....
 
i am using a timer to invoke method and send daily mails.I kept it in Global.asax page.but its not working the timer which i had given is
 
myTimer.Interval = 86400000;
&
myTimer.Interval =1000*60*60*24;
 
i tried these two. if i kept it for 15 min it is working fine. 
 

Thanks in advance....