2 files changed, 108 insertions, 0 deletions
diff --git a/internal/caldata/caldata_test.go b/internal/caldata/caldata_test.go
index 95bb7dc..f993a12 100644
--- a/internal/caldata/caldata_test.go
+++ b/internal/caldata/caldata_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/lukaszkasprzak/lectio/internal/calendar"
+	"time"
 )
 
 func TestUniversalLoads(t *testing.T) {
@@ -473,3 +474,50 @@ func TestTridentineMissalOverrides(t *testing.T) {
 		}
 	}
 }
+
+// TestEFBVMSaturdayReadings pins RG 309(a)'s seasonal selection among the five
+// Missae de sancta Maria in sabbato. Without it the day was kept as Our Lady's
+// office (RG 78) but read the FERIA's Mass -- so a Saturday in Septuagesima
+// announced Our Lady and then read the parable of the labourers.
+//
+// Citations verified by colitur against both photographic scans of the 1962
+// Missal; see its lectionary_ef.ml for the per-formulary scan references.
+func TestEFBVMSaturdayReadings(t *testing.T) {
+	sel := calendar.Selection{Form: "old"}
+	for _, c := range []struct{ date, first string }{
+		{"2026-01-03", "Titus 3:4-7"},     // Christmas Time
+		{"2026-01-10", "Titus 3:4-7"},     // still Christmas Time
+		{"2026-02-14", "Ecclus 24:14-16"}, // after the Purification
+		{"2026-06-20", "Ecclus 24:14-16"}, // Time after Pentecost
+		{"2026-04-18", "Ecclus 24:14-16"}, // Paschaltide -- same first, DIFFERENT gospel
+	} {
+		day, _ := time.Parse("2006-01-02", c.date)
+		layers := []calendar.Layer{Tridentine()}
+		ld := calendar.Compute(day, sel, layers)
+		got := Readings(sel, layers, day, ld)
+		if len(got) == 0 || got[0].Citation != c.first {
+			first := "(none)"
+			if len(got) > 0 {
+				first = got[0].Citation
+			}
+			t.Errorf("%s: first reading = %q, want %q (RG 309(a), the Mass of Our Lady on Saturday)",
+				c.date, first, c.first)
+		}
+	}
+	// Paschaltide shares its first reading with the rest of the year but has
+	// its own gospel -- St John at the Cross rather than the woman in the
+	// crowd. Asserted separately because a first-reading-only test would pass
+	// with the wrong gospel.
+	day, _ := time.Parse("2006-01-02", "2026-04-18")
+	layers := []calendar.Layer{Tridentine()}
+	got := Readings(sel, layers, day, calendar.Compute(day, sel, layers))
+	var gospel string
+	for _, r := range got {
+		if r.Part == "gospel" {
+			gospel = r.Citation
+		}
+	}
+	if gospel != "John 19:25-27" {
+		t.Errorf("2026-04-18: gospel = %q, want %q (the Paschaltide formulary)", gospel, "John 19:25-27")
+	}
+}
diff --git a/internal/caldata/readings.go b/internal/caldata/readings.go
index 3e46ccd..62ef1fc 100644
--- a/internal/caldata/readings.go
+++ b/internal/caldata/readings.go
@@ -2,6 +2,7 @@ package caldata
 
 import (
 	"sort"
+	"strings"
 	"time"
 
 	"github.com/lukaszkasprzak/lectio/internal/calendar"
@@ -56,6 +57,9 @@ func Readings(sel calendar.Selection, layers []calendar.Layer, date time.Time, d
 	// weekday cycle (I/II). Sunday-slugs and weekday-slugs are disjoint, so
 	// trying both cycle suffixes is unambiguous.
 	if sel.Form == "old" {
+		if r := efBVMSaturdayReadings(day); len(r) > 0 {
+			return r
+		}
 		if r := TemporalReadings("old", day.Observed.Slug); len(r) > 0 {
 			return r
 		}
@@ -85,3 +89,59 @@ func Readings(sel calendar.Selection, layers []calendar.Layer, date time.Time, d
 	}
 	return nil
 }
+
+// efBVMSaturdayReadings returns the Mass of Our Lady on Saturday, when that is
+// the day's office.
+//
+// RG 78 keeps the office on a Saturday whose feria is IV class (see
+// temporal_ef.go, which gives the day its white colour). RG 309(a) then says
+// which Mass is said: "Missae de sancta Maria in sabbato ... iuxta temporum
+// diversitatem" -- the Missal prints five formularies and the season selects
+// among them. Without this the day was kept as Our Lady's but read the feria's
+// Mass, so a Saturday in Septuagesima announced Our Lady and then read the
+// parable of the labourers.
+//
+// Citations are colitur's, which verified each against both photographic scans
+// of the 1962 Missal; see its lib/rites/rite_ef/lectionary_ef.ml,
+// bvm_saturday_citations, for the per-formulary scan references.
+//
+// The Advent formulary is included and is STRUCTURALLY UNREACHABLE as the
+// Saturday office: Advent has no IV-class ferias, so the office never falls
+// there. It is kept because RG 309's subject is the Masses themselves, not
+// only the days they land on -- the Mass exists -- and because a missing
+// branch would silently fall through if the rank rules ever changed.
+func efBVMSaturdayReadings(day calendar.LiturgicalDay) []calendar.Reading {
+	// The office, not merely the day: a Saturday IV-class feria that nothing
+	// outranked. A sanctoral feast that won the day keeps its own readings, so
+	// the observed slug must still be the temporal one -- which the office
+	// deliberately reuses rather than replacing (see temporal_ef.go).
+	if day.Weekday != time.Saturday || day.Observed.Rank != calendar.RankClass4 {
+		return nil
+	}
+	if !strings.HasPrefix(day.Observed.Slug, "ef-") || !strings.HasSuffix(day.Observed.Slug, "-saturday") {
+		return nil
+	}
+	first, gospel := "", ""
+	switch day.Season {
+	case calendar.Advent:
+		first, gospel = "Isa 7:10-15", "Luke 1:26-38"
+	case calendar.Christmas:
+		first, gospel = "Titus 3:4-7", "Luke 2:15-20"
+	case calendar.TimeAfterEpiphany:
+		// The Christmastide formulary runs on until the Purification (2
+		// February), not merely to the end of Christmas Time.
+		if m := day.Date.Month(); m == time.January || (m == time.February && day.Date.Day() <= 2) {
+			first, gospel = "Titus 3:4-7", "Luke 2:15-20"
+		} else {
+			first, gospel = "Ecclus 24:14-16", "Luke 11:27-28"
+		}
+	case calendar.Easter_:
+		first, gospel = "Ecclus 24:14-16", "John 19:25-27"
+	default: // Septuagesima, Lent, Passiontide, Time after Pentecost
+		first, gospel = "Ecclus 24:14-16", "Luke 11:27-28"
+	}
+	return []calendar.Reading{
+		{Part: "first", Citation: first},
+		{Part: "gospel", Citation: gospel},
+	}
+}