The sunrise wake up light comes on 30 minutes before the alarm goes off. Personally for me, this feature does not really do anything as I do not see the light come on. The light will gradually gets brighter and may gently wake you up from sound sleep. I have woken up before my alarm and have noticed that the closer it gets to the alarm going off the brighter it gets.
The simulated sunlight can be turned on so that 30 minutes before set time, the light will gradually turn dimmed and turn off at sleep time. This is another favorite feature of mine as I can see the light dimming and I know it is closer to bedtime, without having to look at the clock.
This can be purchased here Amazon.com