First off, in case anyone's not familiar with how to set up a hotkey, here's how:
Scroll down to the User category --> Click New --> Type in the Name, the Description, and the Command --> Click Accept --> Assign New Hotkey --> Save
To use--select a key or multiple keys in the Dope Sheet or Graph Editor, then hit the arrow keys to shift those keys left or right.
Note: You could also just type in "+=(any value)" or "-=(any value)" either in the channel box or the Graph Editor to shift key(s) any specific amount. In addition to adjusting the timing of keys, you could use this trick to adjust transform values of keys as well.