I think a calendar is conceptual because, days, months and years do not actually exist. So I researched the calendar's solar system and found out that it is based on positions of Earth's orbit.
A solar calendar is a calendar whose dates indicate the position of Earth on its revolution around the Sun or, equivalently, the apparent position of the sun moving on the celestial sphere. When the earth rotates, that has own sun's latitude.
Using the solar system, I made Round and Round calendar. I tried to show the sun's altitudes for each of day and set the observer's altitude at 40N° (standard for New York City)