Each circle is one day; each column of circles one month; the twelve columns together represent one year.
Rolled across / wrapped around the surface of the beam this entire calendar is projected onto the surface without overlapping, with the edge of the diagonal pattern spiralling around the beam. Even when more 'months' are added, as long as the parallel diagonals cut across the entire pattern from the beginning to its end, then it will still wrap around the surface without overlapping. With increasing 'time' the spiral becomes increasingly dense and horizontal.
π [pi] / Calendar / Phases Of The Moon - Angular Momentum