Many sites ask for your birth date and hand you back the name of a demon from the Ars Goetia, with its seal and a description. Yet they almost never explain where that result comes from. Here we do the opposite: we investigate the traditions behind it —decans, quinances, the angels of the Shem HaMephorash, the Goetia attributed to "Dr Rudd"— to show what each system answers, what era it belongs to, and what evidence supports it. We don't promise "your true demon": we give you the sources.
For one and the same date, different systems return different entities —sometimes a demon, sometimes an angel— and different results. We don't merge them into a single answer "for simplicity": the difference is the information.
It divides each sign into three decans of 10° and distributes the 72 goetic spirits: spirits 1–36 "by day" and 37–72 "by night." It yields a demon. Crowley published it in Liber 777, which traces the attribution to a manuscript by Mathers in the Golden Dawn. It does not appear in the old grimoires: it is not an inherited tradition. (Going from a date to a degree is approximate, and the sources do not fix when to apply the "day" or the "night" spirit to a person.)
It distributes the 72 Shem angels over ~5-day stretches aligned to the zodiac, anchored at the equinox (angel #1, Vehuiah, rules 20–24 March), each with its psalm and its magical character (its sigil). It yields an angel, not a demon. It is not a 19th-century invention: the day/zodiac distribution already appears in an 18th-century manuscript (Arsenal, Ms 2495), and Lenain states it in degrees ("l'espace de 5 degrés, ou 5 jours"). His actual natal method assigns three genii per person (by day and hour), not one.
We have gone through the complete series, all 72 openings of the manuscript: each spirit appears beside the Shem angel of the same ordinal number, with its seal and its psalm, without finding a single exception. It is an ordinal pairing, not an assignment by birth date; the angel is the spirit's counterpart, not a "natal angel."
It is a system of angels by sign and degree (a list of 360), distinct from the 72 Shem angels and from the 72 Goetia spirits. It is not a table of demons. We include it so it is not confused with the above.
The three systems, where each one comes from with the sources, and why there is no «true demon» for your date.
The names and psalms of the 72 angels already appear in the seventeenth century, in the work of Athanasius Kircher (Oedipus Aegyptiacus, 1652–54). From there, apparently, two branches depart —and we stress "apparently," because the direct dependence is not proven:
Both converge in the Golden Dawn (late 19th c.), and from there pass into Liber 777 (1909) and today's websites. Of those links, only two are documented: that Mathers's Goetia (1904) used Rudd's Hebrew spellings, and that Liber 777 derives from a Golden Dawn manuscript; the derivations from Kircher and Lenain's contribution to the order are plausible, but a hypothesis until collated.
Kircher (1652–54) already carries the names and psalms; Rudd pairs angel↔demon by ordinal number (verified across the whole series, no exceptions); the distribution of the 72 angels over ~5-day/zodiac stretches already appears in the 18th century (Arsenal, Ms 2495), with Lenain (1823) stating it in degrees; Liber 777 distributes the goetic spirits by decan, by day and by night.
The distribution of demons by decan (Golden Dawn / Liber 777, 1909) is 20th-century, reproducible. And joining Lenain's angel to the goetic demon to yield "a demon by date" is a modern synthesis, not an inherited tradition.
An ancient "demon by date" tradition (angel-by-date systems do exist, but not demon-by-date); and any link between decans and the 72 goetic spirits before the Golden Dawn.
When auditing calculators we found that they tend to mix incompatible systems —the 10° decan with the 5° quinance, which diverge from the second spirit onward—, do not cite their real provenance, and sometimes attribute it "to the Lemegeton," which is false: the Lemegeton does not distribute the 72 spirits by decans or by dates. And "72 = 2 × 36" is mere arithmetic, not a demonstrated tradition.
And the calculator? Not yet. The sources come first: we will not publish a "demon by birth" as though it were a demonstrated ancient tradition. That is exactly what the explorer above does: for each system, its rule, its source and its degree of certainty —Lenain's we have completed by hand-transcribing the Arsenal Ms 2495 table (18th c., attr. Blaise de Vigenère); and where a source isn't enough, we leave it pending rather than invent it.
It depends on the system, and none is a demonstrated ancient tradition. The explorer above shows, for your date, which spirit the decan system (Liber 777, 1909) assigns —one by day and one by night— and explains where it comes from. There is no «true demon» by date: we give you the source, its rule and its limits, plus a link to get to know the spirit (its office, its seal and how it was invoked).
Lenain's system (1823), on Arsenal Ms 2495, distributes the 72 Shem angels over ~5-day stretches from the equinox. In the explorer you can see which angel rules your date's stretch, with its psalm. It is an angel, not a demon, and it does not automatically equal the modern «guardian angel» tables.
The historical sources do not prove it. There are systems that distribute angels by date (documented) and distributions of demons by decan (20th c.), but none defines your personality or your destiny. The honest approach is to treat it as what it is: catalogues and correspondences from specific sources, each with its degree of certainty.
→ See also: Is Bune's seal a map of Cyprus? · Chronology of the Goetia · The two streams · What is the Ars Goetia · Myths and confusions
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