Heliochronometer

Or sundial to you and me, but a rather elaborate example accurate to within two minutes.

The bar on the right has a small hole in it, the sun shines through and lights up a small area on the left bar, the months are written on the upper side of the left bar facing the sun, names connected by a line in the form of a very elongated 8.. You angle the device so the spot of light shines precisely on the line with March on it. You then read off the time on the scale shown in the thumbnail.

It worked accurately on this sunny day! I suppose someone has the job of adjusting it tonight when we move to summer time.