Try hitting *#0*# and hitting blue. Take a look at the top where the status bar would be. That am/pm burns right into the screen. Just something to consider...
Sent from my SPH-D700 using Tapatalk
Tried it, but I don't see it. No mark there for me. LCD screens don't burn like old monitors do. It's possible, but difficult to manage. Your screen would have to be consistently on for many hours at a time, regularly, without break, ever. And even then, that's assuming you don't open any full screen app in between.
Here's some more info.