There are very few poems on sundials in the Greek Anthology. A scattering of inscriptional ones are known; you can find out lots about them in the chapter by Francesca Angiò in a collection edited by Evina Sistakou and Antonios Rengakos, Dialect, Diction, and Style in Greek Literary and Inscribed Epigram (2016). The first and shorter of the two poems presented below, 9.780, is in the book; the other is freshly done for this blog.
Ancient timekeeping suited sundials. The day was divided into twelve hours, running from dawn to dusk; the night likewise. from sundown to first light. Summer daylight hours were thus longer than winter ones, summer night-time hours correspondingly shorter, and so on.
The second of the poems makes a pair with its immediate neighbour, 9.807, also on the sundial of Sergius. I expect the seven divisions on its stone dial mark hours of the working day, during which fixed appointments might need to be kept. Martial (4.8) tells us a day's work in Rome wound down in hour five; the eighth hour was when a person might stop in at the gym, on his way from an after-work siesta to 'the dining-couches packed with cushions'; but not everybody could live as easily as Martial did, or aspired to.
On a sundial
A clever stone to compass heavens’ vault:
My little gnomon parses all the sun.
On a sundial
This bounded precinct was an orchard once,
That in its season peeked upon the sun
Through leafy shade that made the day seem night;
But now you see it glitter all serene.
The author of the work was Sergius,
Who witnessed and disclosed the Trinity.
This very stone, erected here, proclaims
Seven instalments of the wheeling sky
That spins forever and inexorably.