Pleiaden-Schaltregel (Pleiades-intercalation-rule)

PLY-ah-den SHAHLT-reh-guhl

babylonian: Pleiaden-Schaltregel (German Assyriological coinage, Schaumberger 1935; the cuneiform rule itself names no single Akkadian title — it is identified by the Moon-and-Stars conjunction-date formulae at MUL.APIN II Gap A 8 - II ii 2)

Definition

The Pleiaden-Schaltregel is Joseph Schaumberger's 1935 designation for the MUL.APIN intercalation rule at II Gap A 8 - II ii 2 that determines whether a Babylonian year is normal or intercalary by the date on which the Moon and the Pleiades (Zappu / MUL.MUL) are "balanced" (LÁL / šitqulū) — in conjunction at the same celestial longitude. In Schaumberger's restoration the year is normal if the conjunction falls on 1 Nisannu and intercalary if on 3 Nisannu; the second subsection fixes normal balance on 15 Tešrītu and intercalary on 15 Araḫsamnu.

In Tradition

Hunger and Steele preserve Schaumberger's coinage while stressing that the first-rule restoration is hypothetical (only day-number 3 of the second statement is preserved). They read LÁL/šitqulū as conjunction-at-same-longitude, rejecting Koch (1997)'s alternative "equal duration of visibility before setting." Brown reads the rule against the grain as "a divinatory device derived from a well known rule of thumb" — a one-month-in-three-years arithmetical scheme retrofitted onto a Pleiades-Moon configuration.

In Practice

For the reader of MUL.APIN II, the Pleiaden-Schaltregel is the first explicit Mesopotamian intercalation discipline: an observational check that triggers a calendrical correction when the ideal-calendar drift exceeds one month. The mechanics are arithmetic — because the Moon advances roughly 13° per day against the stars, a Pleiades-conjunction on day 3 instead of day 1 means the lunar calendar has fallen behind the solar by roughly 30°, requiring a thirteenth month to realign. Hunger and Steele list parallel rules: the fourth tablet of Šumma Sîn ina Tāmartišu gives "if on the 3rd day of Month I you see the Stars and the Moon and they are in balance, this year is normal"; another rule in three Neo-Assyrian copies (Hunger-Reiner 1975) gives the formula "if the conjunction occurs on day (27 − 2n) of month n, the year is normal." Brown reads the contradictions across these schemes as evidence the rule served the EAE Paradigm's divinatory-period-scheme function — retroactive year-typing for omen-prognostication — rather than an empirical calendar-regulation purpose.

Historical Origin

Attested in MUL.APIN II Gap A 8 - II ii 2 (~1000 BCE; Neo-Assyrian transmission), with parallels in Šumma Sîn ina Tāmartišu, ACh. 2 Supp. 19:22f, and the Babylonian Diviner's Manual. Modern treatments: Joseph Schaumberger, *Sternkunde und Sterndienst* Ergänzungsheft 3 (1935) pp. 340-344 — the coinage; Hermann Hunger & John Steele, *MUL.APIN* (Routledge 2019), pp. 331-335; David Brown, *Mesopotamian Planetary Astronomy-Astrology* (Styx 2000), pp. 128-130; Hermann Hunger & David Pingree, *Astral Sciences* (1999), pp. 96-97.

Definition

In Tradition

In Practice

Historical Origin

Further Reading