Learn

Five short pages, in the order the ideas build on each other. Each one stands alone, but together they explain everything on the figure.

1. The seasonsEarth’s tilted axis gives us solstices, equinoxes and seasons of unequal length. Start here.
2. How long is a year?The year of the seasons, the year against the stars, and why they differ by twenty minutes.
3. The equation of timeWhy a sundial runs up to a quarter of an hour ahead of the clock or behind it, and when it peaks.
4. The analemmaPut the two together and the noon Sun traces a lopsided figure eight across the year.
5. The namesEarlysun, Evensun, Longsol, Echosun and the rest: the turning points of the clock and the orbit, named.

Tools and sources

• QuestionsShort answers: the earliest sunset, the closest Sun, the sundial and the clock.
• Time betweenThe exact gap between any two moments, 1900 to 2100.
• CalendarEvery moment in your own calendar, at its exact time.
• DataEvery moment from 1900 to 2100, as CSV or JSON.
• MethodologyHow each moment is computed and checked.