Source-verification research. The scholarly sourcing, citations, and contested points behind this technique — pure research, with no implementation detail. For the curated summary of what Stellium implements (defaults, the forks it chose, simplifications) and how these sources map to the code, see ../README.md.

FIRDARIA: Sources, Values, and Contested Points¶

TL;DR¶

The period values are stable and near-universal across all sources (Sun 10, Venus 8, Mercury 13, Moon 9, Saturn 11, Jupiter 12, Mars 7, North Node 3, South Node 2 = 75 years); the day-order (Sun-first, Chaldean) is undisputed. The one genuine mechanical fork is where the lunar nodes fall in nocturnal charts: Abu Ma’shar / al-Qabisi (as correctly read) / al-Biruni / Robert Hand / Birchfield put both nodes at the very end (after Mercury, ages 70–75); Bonatti (as read by Zoller and much modern software) puts them after Mars (ages ~39–44).
Sub-periods are standard: each planetary major divides into 7 equal sub-periods in Chaldean order starting from the major-period ruler; nodes neither subdivide nor participate as sub-rulers. A modern minority variant (Aswin Subramanyan’s “AB Method”) uses proportional/weighted sub-periods and includes the nodes as participants.
The dominant and earliest position is Abu Ma’shar’s: nodes at the end (both sects), seven equal sub-periods from the major ruler, node majors non-subdividing, the cycle repeating past 75, reckoned in real (365.2425-day) years. The nocturnal-node question is genuinely unresolved — Bonatti (nodes after Mars) and the modern AB Method (proportional sub-periods, participating nodes) are the principal alternatives, and practitioners are split.

Key Findings¶

1. Origin and transmission. Firdaria (Arabic firdāriyya, pl. firdāriyyāt; Persian firdār/fardār; Latinized alfridaria/alfridaries via the article al-) is a Persian-transmitted time-lord system. The word is standardly said to derive, via Persian, from Greek periodos (“period”) — the initial Greek “p” shifting to “f” in Persian; this derivation is stated explicitly by, e.g., The Attasio School (“the name comes from the Greek firdar περιοδος – period adapted to Persian – al firdariya”) and The Astrology Project (“the term firdaria… was a translation of the Greek word period”), though it is repeated rather than rigorously documented. The earliest surviving natal accounts trace to al-Andarzaghar (7th c., in the Book of Aristotle tradition and al-Dāmaghānī’s later compilation), then to Abu Ma’shar al-Balkhī — full name Abū Maʿshar Jaʿfar ibn Muḥammad al-Balkhī, Latinized Albumasar, born in Balkh, Khorasan (modern Afghanistan) 10 August 787 and died in Wāsiṭ, Iraq 9 March 886 — whose On the Revolutions of the Years of Nativities is the fullest early source. There is no attested Hellenistic Greek firdaria; the technique appears first in the Perso-Arabic material, though it belongs to the same broad family as Hellenistic period systems (decennials in Firmicus, Valens’s ascensional-time chronocrators) and the Indian dashās. The node participation is widely believed by scholars and practitioners to be an Indian-derived feature.

2. Period values (confirmed against every source). Sun 10, Venus 8, Mercury 13, Moon 9, Saturn 11, Jupiter 12, Mars 7 (seven planets = 70 years), plus Head/North Node 3 and Tail/South Node 2 (total 75). Abu Ma’shar (Dykes trans.): “the fardār of the Sun is 10 years, the fardār of Venus 8 years… Mars 7 years, the Head 3 years, and the Tail 2 years: the amount of all of that is 75 years, then it returns to the Sun.” Al-Qabisi, al-Biruni, Bonatti, Schoener, Ibn Ezra, and Lilly all agree on these numbers. No credible source gives different period lengths.

3. Day/night ordering (sect). The sequence is strictly in Chaldean order (descending: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), begun from the sect light. Diurnal: Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars (then nodes). Nocturnal: Moon, Saturn, Jupiter, Mars, Sun, Venus, Mercury (then nodes). This is undisputed for the seven planets in both sects.

Details¶

The node controversy (the central methodological fork)¶

This is the one substantive disagreement, and it affects only nocturnal charts.

Abu Ma’shar (the primary source): In On the Revolutions of the Years of Nativities, Book IV ch. 7 (Dykes translation): “Now, the Head and Tail distribute for diurnal nativities after the years of Mars, and for nocturnal nativities after the years of Mercury: and it is when the native enters year 71 — and he will begin in the distribution of the fardārs with the Head, then the Tail, whether the native was diurnal or nocturnal.” So the nodes ALWAYS come last (ages 70–75), in both sects. The independent al-Dāmaghānī quotation of al-Andarzaghar gives the identical rule.
Al-Biruni (Book of Instruction in the Elements of the Art of Astrology, R. Ramsay Wright trans., London: Luzac, 1934, §446–447 “Periods (FIRDARIA) of control of Human Life”): confirms the same values (Head 3, Tail 2, total 75) and the nodes-at-end position, following Abu Ma’shar. He uses “Head”/”Tail” of the Dragon for North/South nodes and gives the diurnal order beginning with the Sun and the nocturnal beginning with the Moon.
Al-Qabisi (Introduction to Astrology IV, Dykes trans.): for the diurnal case explicitly lists “…Then the Head, then the Tail, then you come back to the Sun.” For nocturnal he says only “begin the governance from the Moon… Likewise planet after planet, as we described in the section on the Sun” — he does NOT spell out where the nocturnal nodes go. This omission is the root of the confusion.
Bonatti (Liber Astronomiae, Tractatus de nativitatibus ch. III): paraphrases al-Qabisi almost verbatim, saying the nocturnal disposition begins from the Moon “and will be in all respects as was explained when it began from the Sun both regarding the participation of the planets… and regarding the succession of them in the order of the circle.” The ambiguous phrase “in all respects” was read by Robert Zoller to mean the nodes keep the same slot relative to the start — i.e., after Mars — which in a nocturnal chart falls at ~ages 39–44.
Modern split: Robert Hand (ARHAT), Steven Birchfield, and most historically-minded astrologers hold the nodes belong at the end (70–75) in both sects, treating the Bonatti “after Mars” reading as a transmission artifact from Bonatti’s lack of access to Abu Ma’shar’s fuller text (not translated to Latin until after Bonatti’s death). Robert Zoller and his students (e.g., Regulus Astrology) defend the “after Mars” placement on empirical grounds. Several software packages and calculators (including some following the “Bonatti/Dykes” nocturnal labeling) place the nodes after Mars.

Do the nodes participate at all?¶

Some practitioners drop the nodes entirely and use only the seven planets (a 70-year run before repeat). Where used, the nodes get their own major periods (3 and 2 years) but — per Abu Ma’shar — “they do not partner with the planets (nor do the planets partner with them), because they do not have houses.” So in the classical scheme the node majors are NOT subdivided into sub-periods, and the nodes do NOT appear as sub-rulers within planetary majors. Head = Caput Draconis / North / ascending node / Rahu (3 yrs); Tail = Cauda / South / descending node / Ketu (2 yrs).

Sub-periods (“second firdaria”)¶

Standard rule (Abu Ma’shar, al-Qabisi, Bonatti, Schoener, Hand): each planetary major divides into 7 equal parts (each = major/7). The first sub-period is ruled by the major ruler itself; the rest follow in Chaldean descending order from that ruler, wrapping around. E.g., Sun major → Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars. Abu Ma’shar: “it stands alone in indication at first, for an amount of one-seventh of its years, then after that the rest of the planets partner… the one which partners with it the first time is the planet which is below it in the celestial circle.” Sub-period ORDER is thus Chaldean-descending-from-the-major-ruler — the SAME rotational logic as the major sequence, not the day/night firdaria order. There is essentially no genuine classical disagreement on sub-period order; the apparent “Bonatti vs Abu Ma’shar” sub-order dispute is really the node-placement issue bleeding into perception.
Division method — equal vs weighted: The classical texts use EQUAL sevenths. A modern variant, Aswin Balaji Subramanyan’s “AB Method” (2019; developed in his book Firdaria: Periods of Life, ISBN 9798596115895, whose Ch. 3 translates the firdaria section of the 11th-c. Tunisian astrologer Al-Rijal’s Kitāb al-Bāriʿ fī Aḥkām al-Nujūm), replaces equal division with proportional division: a sub-ruler’s share = (major years × sub-ruler’s own firdaria years) / 75, and it includes the nodes as participating planets (so 9 sub-periods, not 7). His stated rationale: if the 75-year total is significant, the nodes’ contribution to it must be too, so they should participate in sub-periods. This is implemented in Delphic Oracle (Curtis Manwaring) as the “AB Method” and in Planet Dance (Jean Cremers) as “AB Method – Hand” and “AB Method – Zoller.” It is a minority modern innovation, not a classical convention.
Deeper levels: The classical firdaria stops at two levels (major + sub). Robert Hand notes: “This does not seem to have been true of the firdar where we only have the long-period ruler and the short-period subruler.” No standard third level exists.

Starting point, direction, repeat¶

The sequence always begins at birth (age 0) with the sect light’s ruler (Sun by day, Moon by night), regardless of any other chart factor. It proceeds forward in fixed order. After 75 years (or 70 if nodes omitted) it repeats from the beginning — Abu Ma’shar: “then it returns to the Sun.” Schoener explicitly delineates a Sun-Sun period recurring after age 75. Whether nodes are included in the repeat follows whatever node setting is chosen.

Year length and date conversion¶

The classical texts do not specify a day-count; they speak of “years.” Modern implementations diverge: the astrology-api.io service uses 365.2422 (mean tropical year); others use 365.2425 (Gregorian mean) or 365.25 (Julian). The Perso-Arabic astronomical context worked with real solar years (the Zīj tradition), not the ideal 360-day year — the 360-day “year” belongs to the mundane “mighty fardar” (1°/year across the zodiac) and to some Vedic savana-year usage, not to natal firdaria. For calendar output, most practitioners count real years from the birth moment. This is a genuine divergence but a low-stakes one: over 75 years, 365.25 vs 365.2425 differ by under a day.

Interpretation conventions¶

A period is judged by the natal condition of its ruling planet: essential dignity, house occupied and ruled, aspects, and sect status (an out-of-sect or debilitated firdaria lord is judged more harshly; a Mars period is worse for a day chart, Saturn worse for a night chart). The major (“lord of the period”) and sub-ruler (“partner”) combine — Robert Hand cites the idea (via Darrelyn Gunzburg / his Australis ‘97 workshop) that the major ruler is “Matter” and the sub-ruler “Form.” When the two are configured (aspecting) in the natal chart, their combined period is intensified; a planet natally aspecting the firdaria lord is also “activated.” Schoener’s Three Books on the Judgment of Nativities (Book III ch. 8) provides a complete set of two-planet delineations (translated in Hand’s ARHAT booklet), and the Liber Aristotilis offers parallel material. The nodes, when ruling, are read as Head = generally fortunate/gainful, Tail = troubles and loss.

Relationship to other techniques¶

Firdaria is a long-range “background climate” chronocrator, sitting above annual profections, solar revolutions, and zodiacal releasing in the timing hierarchy (Abu Ma’shar ranks it above the solar-revolution lord). It is closely analogous to the Vedic Vimshottari dashā — both are unequal planetary periods run sequentially — but they differ. Vimshottari is established in the Brihat Parashara Hora Shastra (ch. 46) as the “universal” dasha; its name is Sanskrit for 120 (its total length in years), and its period values are Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17. Per Phala Dīpika 19.4, its dasha year is “the astronomical solar year of 365.25 days,” reckoned from the Sun’s return to its natal position, and the first mahadasha is the lord of the Moon’s janma nakshatra — i.e., it starts from the Moon’s nakshatra, not from sect. Scholars (Pingree, and practitioners like Hand) note the shared “planetary period” family and probable ultimate Babylonian/Indian influence, but firdaria is not a direct derivative of Vimshottari.

Tropical/sidereal and unknown time¶

Firdaria is purely time-based, not position-based, so the tropical/sidereal zodiac choice does NOT affect the period calculation itself (it only affects the natal-chart interpretation layer). The one hard requirement is sect: the calculation cannot start without knowing day vs night, which requires at least an approximate birth time and location. Near sunrise/sunset (within ~10 minutes) sect can flip and invalidate the entire downstream sequence; for genuinely unknown times, no reliable firdaria is possible and rectification is required.

The positions in the tradition¶

The seven-planet order and the period values are undisputed; the schools differ only on the nodes and on how sub-periods are divided.

Abu Ma’shar / Persian — nodes at the end in both sects (ages 70–75), seven equal sub-periods from the major ruler, node majors non-subdividing, cycle repeating past 75, real (365.2425-day) years. The fullest and earliest primary source, and the position with the strongest historical and modern-scholarly support (Hand, Birchfield). Often labelled “Al-Biruni” in software (e.g. Janus), since al-Biruni follows the same nodes-at-end order.
Bonatti / Zoller / Lilly — nocturnal nodes after Mars (ages ~39–44), otherwise as above. The dominant reading in the Latin/Renaissance line and in Zoller-lineage modern practice; matches many existing calculators. It rests on an ambiguous al-Qabisi paraphrase rather than an explicit statement.
AB Method (Subramanyan, 2019) — the nodes participate as sub-rulers (nine sub-periods) and sub-periods are divided proportionally (share = major × sub-years / 75). A minority modern innovation, not a classical convention; implemented in Delphic Oracle and Planet Dance.
Seven-planet (no nodes) — a 70-year cycle, used by practitioners who reject the (Indian-derived) node periods.

The settled points: sub-period order is Chaldean-descending from the major ruler (unambiguous across sources); the classical sub-period division is equal (major/7); the 360-day year is not appropriate for natal firdaria (it belongs to the mundane “mighty fardar”); the sequence repeats past 75 (Abu Ma’shar’s “returns to the Sun”; Schoener delineates the recurrence). Sect is a hard requirement — near sunrise/sunset it can flip and invalidate the whole sequence.

What would revise these findings¶

If a future authoritative critical edition or a strong body of empirical rectification work were to vindicate the Bonatti “after Mars” reading, it would gain a stronger claim than the currently-dominant nodes-at-end position; if the AB Method accumulated broad practitioner adoption and validation, proportional division would move from a minority innovation toward a mainstream alternative.

Caveats¶

The strongest primary quotations here (Abu Ma’shar Book IV, al-Qabisi IV) come through Benjamin Dykes’s and Steven Birchfield’s translations; the al-Biruni wording is anchored to the Wright 1934 translation’s contents (§446–447) plus near-verbatim secondary quotations, not a re-verified page scan (the exact printed page ~259–260 is consistent with the pagination but was not confirmed against a live scan).
The “who is right” on nocturnal nodes cannot be settled textually beyond noting that Abu Ma’shar’s explicit statement favors nodes-at-end and Bonatti’s is ambiguous; the “after Mars” reading is defended on practice, not text.
Etymology from Greek periodos is the standard account but is described by some (e.g., the Attasio school) as unproven; the derivation is plausible and widely repeated rather than documented.
Many modern web calculators and app write-ups repeat each other and should be treated as tertiary; the reliable anchors are the Dykes translations (Persian Nativities III & IV; al-Qabisi Introduction; Dorotheus Carmen), Robert Hand’s ARHAT article “Firdar, Alfridaria, or Alfridaries” (with Schoener’s tables and delineations), Steven Birchfield’s The Fardārāt in Nativities, David Pingree’s The Thousands of Abū Maʿshar (1968), James Holden’s A History of Horoscopic Astrology, and the primary critical editions (Wright 1934 for al-Biruni; Burnett/Yamamoto/Yano 2004 for al-Qabisi; Yamamoto/Burnett Brill 2019 for Abu Ma’shar’s Great Introduction).