how to set the delay on for 7 hours? For my application I need to simulate the sunlight including the rising and setting of the sun.

I have a program that will light up some LEDs slowly over a period of time but I need to know what to type in the (delay on) to keep the lights on for 7 hours? 

Will it work if I just replace delay(1000) with delay(25200000UL) ?
I don't want to run anything else at the same time and don't want to use or understand millis().
Thanks for any help.
Yes, absolutely, it should work. But your code will be easier to read if
you use some constants, like:

const unsigned long SECOND = 1000;
const unsigned long HOUR = 3600*SECOND;

delay(7*HOUR);