Dial of Days

Now

Universal Time

Julian Day: every day since 4713 BC, counted without a gap. The number turns over at noon.

The same day, otherwise named

Real time

Sizes and distances are not to scale.

What is exact here

Computed for the instant shown: the Earth's place on its orbit, its tilt and spin, the line between day and night, the Moon's direction and phase, the stars behind, every date and the day count.
Not to scale: sizes and distances. The Sun, Earth and Moon are drawn far larger than they are, and the Moon far closer.
Still pictures: the clouds and city lights are one snapshot. Real weather is not shown, and the lights fade out before the 1880s.
The instrument in the orbit view is a modelled frame. Its rings are centred on the Earth's orbit, not on the Sun: the orbit is very nearly a circle, but the Sun sits a little off its centre. In our era the Earth passes nearest the Sun in early January; five thousand years ago it did so in October. Every tick, name and digit on the instrument is placed by calculation. The ten notches beside the hand are the ten date labels skipped in October 1582. The red jewels round the base and the toothed crown are decoration.
Before clocks, the Earth's spin is known only to minutes. The brass wedge on the globe shows how much.