Tasker is great but way to complex to learn if you only want to shut off sounds at night.
I use a free app called Profile Scheduler. I think the "Silent" profile was pretty much setup how I needed it and all I needed to do is set the times. You can create profiles for movie theaters, cars, planes, meetings etc... if you wanted.
I have the Silent profile turn off wifi, data, sounds etc.. from 11:30pm -7:29am. So at 7:30am everything is turned back on so my alarm can start up to the sound of my Pandora morning music station.
One thing I wish it did was turn off the LEDs during that time so I did not need to put my phone face down at night.