Sky tab › hourglass: the sky for the same date and time in any year from 3000 BCE to 3000 CE.
- Stars: bsc5.json gains proper motion (VizieR V/50 pmRA, pmDE, arcsec/yr; pmRA already × cos dec), applied linearly from J2000. Precession and nutation come from Astronomy Engine's EQJ→HOR rotation for the date, as before.
- Header shows the year, the pole star (brightest-nearest star above mag 3.7 to the visible pole) and its distance, and "Back to today". The tonight bar is hidden while another year is shown.
- Year sheet: steppers by 100 and by 1, and moments (Great Pyramid 2560 BCE, Almagest, 1054 supernova, Galileo, Apollo 11, Polaris closest in 2100).
- Dates before 1582 are Julian (Foundation's Gregorian calendar). Planet positions far from today are approximate.
- Tests: Polaris < 0.55° from the pole in 2100 and > 10° in year 1; Thuban < 1° in 2800 BCE; Arcturus moves 1.27° in 2000 years.
Library.page(hr:)added.