Put it on a flat and horizontal surface and orientated to the North.
Use the top of the shadow to read date and hour.
Use it to know the date :
The upper line is the Winter Solstice (December 21st)
The downer line is the Summer Solstice (June 21st)
The middle line is the Equinoxes (March 21st / Sptember 21st)
Use it to know the hour :
You will need to correct the solar time if you want to know the UTC.
Add 1h in Winter and 2h in Summer if you have a seasonal correction of the time (such in West Europe)
Add (west) or remove (east) a correction according to the distance with your reference meridian (10min for 200km at 45° latitude)
Praha : +1h (Summer) / +0 (Winter) - Paris : +1h50 (Summer) / +50min (Winter) - Torino : +1h30 (Summer) / +30min (Winter) - Istanbul : +1h
Example : June 10th in Dinan (West France / 48°) : 18h20 (solar) + 2h (Summer) + 10min (west of meridian) = 20h30 UTC
Use it to measure the Solstices :
During the Winter Solstice, at 12h (solar time) the light will go through the 3 "horizontal" upper holes. You should see a light point on the table behind the sundial.
During the Summer solstice, at 12h (solar time) the light will go through the “vertical” hole.
M4NU
