HOW TO READ THE MERIDIAN
1. Year of implementation
2. Winter Solstice, with its zodiac sign. The shadow of the Gnomon’s tip moves from this point on 22 December
3. Summer solstice (twins) 21 June
4. Equinoctial line: the shadow of the tip of the Gnomon moves on this line on two occasions, the spring equinox (March 22) and the autumn equinox (September 23).
At the two opposite points of the line its zodiac signs are marked.
The meridian indicates the solar hour, local hour.
The central meridian of the time zone which affects Italy crosses the Etna (15° East of Greenwich).
The distance of Viareggio from the meridian of Mount Etna is 4° 44 ′ pariah (since the longitude of Viareggio is 10° 15 ‘). Because the Sun (apparent motion) takes 4 minutes in a degree, will take 18 minutes to be on Viareggio’s vertical. The Sun moves from East to West, then reaches the meridian of Viareggio 18 minutes after being found on the meridian of Mount Etna. The time indicated by the Sundial, corrected with the addition of 18 minutes, should be further modified with additions or subtractions due to the equation of time, for each day of the year (see table below).
With the Sundial in Viareggio, on 5 may, when marking the noon,
the wristwatch will be the conventional 13.16 (considered daylight, in addition hour).