Delay of LCD and delay of Relay

Hi, i am using arduino to do a project. The problem is ,the LCD cannot display out the reading every 3 second, it will follow the delay time of Relay = 6 hours, can anyone give some suggestion, thx...

Cheers, Jason

With millis() you can do all different kind of timings at the same time.
Start with this :
This can be useful :

ok thx u Peter_n