If you want to shift all the keyframes at the same time, just open the layers so you can see the keyframes and the drag select them all and the move them all at the same time.
If you want to stagger them (or sequence them) so that something happens in layer 1 for 1 second and then that same something happens in layer2 but 1 second after the first, you can select all the layers you want to stagger (select from top down and the top layer will be the earliest layer) then right click on one of the layers and choose keyframe assistant. In there you will find sequence layers. Turn that on and pick the amount of overlap you want the offset to be. So if all your layers art 5 seconds long and you choose an overlap of 4 seconds, each layer will be 1 second later than the one before.
I final way, assuming you cant move the footage in time is to just copy and past the keyframes from one layer to another – wherever you put your time marker is where the keyframes will get pasted in the next layer no matter where they were in the layer you copied them from.
Just remember to delete the old keyframes if you already have them there. You can also do this within the layer itself – copy keyframes, delete keyframes, move time slider, paste keyframes.
You can do this to multiple attributes at the same time. AE knows that position data needs to go to the position attribute and trani data needs to go to trani attribute.