feat(ef): implement the calendarium's bissextile February shift

2026-08-22T14:40:24Z

The Missale Romanum's calendarium footnote for February (LT.txt:5011-5014, scan-corroborated scan2.txt:3050-3058): in a leap year the sixth kalends of March (24 February) is doubled rather than a 29th day appended, so St Matthias moves 24->25 February and St Gabriel of Our Lady of Sorrows 27->28, with 24 February itself carrying no fixed office that year. data/ef/expected-divergences-lms.sexp entry L3 tracked this as an open gap. Implemented as the rubric's own general mechanism (every fixed entry from 24 through 28 February shifts one civil day later in a leap year), not as "move these two named saints": the two readings are indistinguishable on shipped data (nothing else is fixed in that window) and diverge only for a future --overlay entry in the same range, which the mechanism reading covers correctly and a two-saints special case would not. This project has already been bitten once (RG 16(a)) by a rule implemented against shipped data's coincidental shape rather than the rubric itself. Kernel stays rite-agnostic: Rite.t gains a fixed_key field (Date.t -> (int * int) option), the same seam easter already establishes, read only by Layer.on_date's FIXED half -- the movable half (Easter_offset/Nth_weekday) is untouched. Default is the identity mapping, an optional argument on on_date, so every existing caller and every rite that supplies nothing is byte-identical to before this field existed. Date.is_leap is exposed in date.mli (already existed in date.ml) so the rite reads the kernel's own single-sourced leap-year definition. The EF implementation lives in Rite_ef.Temporal_ef.bissextile_fixed_key, fully cited, wired into Rite_ef.context. Blast radius, measured over the full 1583-9999 domain (Calendar.year run twice per civil year, real fixed_key vs identity, every day diffed): all 2,041 leap years in the domain show a visible change for each saint; 6,983 individual liturgical days change total, zero unclassified, across four shapes (Matthias vacates 24 Feb in 1,803 years / occupies 25 Feb in 1,811; Gabriel vacates 27 Feb in 1,699 / occupies 28 Feb in 1,670). L3's own prior estimate (1,650 years, observed-outright only) is confirmed close on the same definition (1,677 measured); the broader observed-or- commemorated count is higher, not lower, showing the narrow estimate undercounted visible impact rather than overcounting it. The lectio differential (2005-2050 fixture) gains a new cited entry, C40 in data/ef/expected-divergences.sexp: lectio implements no such shift, so every leap year in its window now diverges on the two shifted days (21 rows, not the naive 44 -- the comparator never compares commemorations, so a side where the shifted saint has zero comparator-visible footprint on both engines produces no row). The LMS Ordo's 2023-2024 fixture -- the window L3 was originally found in -- now matches on the Creed comparison; its formulary-override bucket count is corrected 182->181 (24 February leaves the counted Proper population, becoming Own_slug-sourced). The missalemeum oracle fixtures (2026-2027, 2038, 2035) cover no leap year and are unaffected. L3 is closed: converted from an active allow-list record to a prose closure paragraph (L1's own precedent), citation preserved verbatim, fix and measured blast radius recorded. The id-list assertion narrows to [L4] alone, and the now-dead "2024-02-24" -> "L3" date mapping is removed. Six golden values pinned across four new test cases: Matthias in a leap year (both the vacated and occupied sides) and a common-year control; Gabriel likewise, deliberately choosing a leap year where he is admitted only as an ordinary commemoration rather than winning outright, a different shape from Matthias's. Mutation-tested: forcing fixed_key back to identity reddens exactly five test cases -- the differential's Layer C count-pin (C40 drops to 0 actual vs 21 expected), the LMS Ordo's Creed and formulary-bucket checks, and both new golden pins -- confirming the tests actually exercise the fix. Reverted; dune test, the exhaustive sweep, and make check are all green.

kernel(date): ISO-8601 rendering, validating parse, sexp converters

2026-08-11T09:15:18Z

Adds sexplib and ppx_sexp_conv to the project and wires the ppx into the kernel library. Date's sexp form is an ISO-8601 atom rather than the opaque rata die, so data files stay human-editable and parsing revalidates the 1583..9999 domain.

kernel(date): proleptic Gregorian date, validated make + arithmetic

2026-07-31T12:04:22Z

Hinnant civil<->days rep (1970-epoch rata die); make validates month/day and the 1583..9999 domain; of_rata/add_days are total arithmetic. Weekday, compare. Tested: known weekdays, leap boundaries, rejects; qcheck round-trip / add-inverse / weekday-cycle properties over random in-range dates.

colitur.git/lib/kernel/date.mli, branch v1.2.1

feat(ef): implement the calendarium's bissextile February shift

kernel(date): ISO-8601 rendering, validating parse, sexp converters

kernel(date): proleptic Gregorian date, validated make + arithmetic