Sundial of the month May

Vertical sundial
Alkmaar

The sundial pictured here is on the south wall of the St. Laurenskerk (Church of St. Lawrence) in Alkmaar, in the province of North Holland.
It is an exact south dial, but the wall itself is not exactly east to west, and the sundial is obliquely bricked into the wall.
The sundial is dated 1781.

The sundial shows local apparent time. There are seven date curves, corresponding to the twelve signs of the zodiac.
Furthermore, vertical lines indicate points of the compass. Three are marked ZO, Z and ZW, meaning southeast, south and southwest.