# topics/chronology — line them up

Kieran, 2026-09-08: "if you're talking about cycles of Halley's comet or eclipses... line them up.
for real. there's def no unbroken world history lineage from first principles."

## First test: the Spring and Autumn Annals against the computed sky

**Record.** The 春秋 jing text as transmitted on zh.wikisource (12 dukes, fetched 2026-09-08,
`sources/wikisource/`, revision ids in the manifest). 37 entries say 日有食之 ("the sun was
eaten"); 31 carry a sixty-day cycle day; reign-years total 242 by the text's own count.
Parsed by `pipeline/` (see `derived/chunqiu_eclipses.json`). Nothing taken from a concordance:
no BCE year, no month table, no cycle anchor.

**Sky.** Solar eclipses from orbital mechanics (astronomy-engine, VSOP87/ELP), no calendar assumed;
restricted to eclipses visible at Qufu (35.6 N 117.0 E), the capital of Lu, on the local date.

**Search.** Two free parameters, exhaustively: the astronomical year of Duke Yin's first year
(−1000 to −442) and the phase of the sixty-day cycle (60). A record matches a cell when an
eclipse visible at Lu falls in that reign-year, within a month of the stated Zhou month
(Zhou month 1 ≈ December/January), on a day whose cycle name is the one stated.

**Result** (`pipeline/align.py --local --slack 0`, `derived/align_chunqiu_local.json`):

| first year of Duke Yin | matches of 31 | note |
|---|---|---|
| −721 (722 BCE) | 21 | the conventional date; rank 1 of 33,540 cells; z ≈ 53 |
| −667 (668 BCE) | 15 | 54 years later: the exeligmos (three saros) alias |
| −775 (776 BCE) | 14 | 54 years earlier: same alias |
| everything else | ≤ 11 | null mean 0.05 |

The ten misses at −721: seven have no eclipse visible at Lu in the window (either an error in the
annal, an eclipse reported from elsewhere, or the visibility model's ΔT at the horizon); three are
cycle-day mismatches, two of them the known duplicate entries where the annal records eclipses in
consecutive months (襄公 21 months 9 and 10; 襄公 24 months 7 and 8), which the sky cannot do.
Nobody was assumed error-free; the errors are the minority and the alignment holds without them.

**The cycle phase** at the peak is 49, which implies, if the sixty-day count has run unbroken,
that 1 January 2000 was a 戊午 day. Any Chinese almanac can confirm or refute that; if it
confirms, the day count runs unbroken from Lu to now, from first principles.

**Caveats, left visible.** The local-visibility criterion depends on the model's Earth-rotation
history (ΔT), which is itself partly fitted to ancient eclipse records; the year alignment does
not depend on it (the 54-year aliases do not move with ΔT). With eclipses anywhere on Earth
instead of visible ones, the test aliases badly (six first-years tie). The month mapping is
approximate (Zhou intercalation). Cross-check against JPL DE422 pending (`data/ephemeris/`).