The position of the Earth's terminator (the boundary between night and day) is adjusted for the seasons.
The upper pusher advances by a day, the lower one by an hour.
The (fictitious) starry background rotates once a year relative to the Sun. Though Alexandria has no date windows the approximate times of the solstices, equinoxes, and apsides for dates within a few decades of the present are indicated by the position of the Sun relative to some tiny star patterns on the front side:
|Mar 20||Equinox||beginning of northern spring|
|Jun 21||Solstice||beginning of northern summer|
|Sep 22||Equinox||beginning of northern fall|
|Dec 21||Solstice||beginning of northern winter|
|Jan 4||Perihelion||Earth closest to the Sun|
|Jul 4||Aphelion||Earth farthest from the Sun|
Of course, this display is wildly out of scale!
The distance to the Moon is roughly 30 Earth diameters, to the Sun more than 7000.
|Equation of Time|
|Vernal Equinox Angle|
|Moon Age Angle|