Be resting in the same room as the Solar Altar at 6:00am, be sure to go early so you are there in time.
The Solar Altar is the same room you obtain the Mark of Irresponsibility, directions can be found in the Solar Altar miniquest guide.
WARNING: Entire zone is CPK and no-recall, do not take items you are not prepared to lose. The Solar Altar room does fire damage, so be sure to watch your health.
For experiencing the start of a new day in such unusual fashion, the Powers have granted thee a Mark. You have been granted The Mark of Dawn! You gain 56 practices!
Addendum: Went in with a form on 9/28/11. Only I got the mark. It's randomly granted to only one person resting in the room. --Sanger