Double clic on your layer to open the layer view. From here you can use the pan behind tool to change your anchor point without screwing your entire animation
Yeah, that was my first thought. But I have a whole bunch of squares aligned and I don't want to eyeball them all.
Is there any numerical way?
To easier the process and be shure your anchor point is in the middle press Shift while moving your anchor point with the pan behind. It will increment full units. Look in your infor paete, when the value says 0,0 your right in the middle.