The image below is the base of the calculator. Print this image on thin card.
The image below is the Solstice/equinox marker wheel. Print this image on to thin card and cut round the dotted line.
Fix the center of the wheel to the center of the base with a stud of some kind. You could paste the base onto a cork tile and fix the wheel with a drawing pin.
As any Pharaoh of ancient Egypt could tell you, finding the sky for any era is a cinch.
The other markers give you the other equinox and solstice constellations. For example, if the spring equinox marker is set to Leo, (about 10-12000 years ago), then the autumn equinox would be Aquarius, the summer solstice would be Taurus, the winter solstice would be Scorpio.