2 files changed, 35 insertions, 0 deletions
diff --git a/internal/calendar/temporal_ef.go b/internal/calendar/temporal_ef.go
index a043179..6828f35 100644
--- a/internal/calendar/temporal_ef.go
+++ b/internal/calendar/temporal_ef.go
@@ -422,6 +422,15 @@ func efWeek(date time.Time, season Season, y int, easter time.Time) int {
 		// its ferias. Epiphany itself is a feast inside Christmas Time (RG 72),
 		// not the head of a numbered week.
 		return daysBetween(firstSundayAfterEpiphany(y), date)/7 + 1
+	case Passiontide:
+		// Passiontide is TWO weeks and they are not interchangeable: Passion
+		// week (from Passion Sunday, Easter-14) and Holy Week (from Palm
+		// Sunday, Easter-7) have entirely different Masses. Numbering them
+		// both 0 -- which is what falling through to the default did -- gave
+		// every day of Holy Week the slug of its Passion-week namesake, so the
+		// two weeks shared one set of readings and Holy Week could not have
+		// its own.
+		return daysBetween(easter.AddDate(0, 0, -14), date)/7 + 1
 	case Septuagesima:
 		return daysBetween(easter.AddDate(0, 0, -63), date)/7 + 1
 	case Easter_:
diff --git a/internal/calendar/temporal_ef_test.go b/internal/calendar/temporal_ef_test.go
index e8ef391..d930cc7 100644
--- a/internal/calendar/temporal_ef_test.go
+++ b/internal/calendar/temporal_ef_test.go
@@ -334,3 +334,29 @@ func TestTemporalEFRogationDays(t *testing.T) {
 			"commemoration cannot be built here without displacing the Vigil", got.Cel.Slug)
 	}
 }
+
+// TestTemporalEFPassiontideWeeks pins that Passion week and Holy Week are
+// numbered apart. They are two weeks with entirely different Masses, and
+// efWeek used to give both 0 -- so every day of Holy Week took the slug of its
+// Passion-week namesake and the two shared one set of readings.
+//
+// Good Friday is the case that shows why it matters: it was reading Passion
+// Friday's Mass.
+func TestTemporalEFPassiontideWeeks(t *testing.T) {
+	easter := d("2026-04-05")
+	for _, c := range []struct {
+		off  int
+		slug string
+	}{
+		{-13, "ef-passiontide-1-monday"}, // Passion week
+		{-11, "ef-passiontide-1-wednesday"},
+		{-6, "ef-passiontide-2-monday"}, // Holy Week
+		{-2, "ef-passiontide-2-friday"}, // Good Friday
+	} {
+		day := easter.AddDate(0, 0, c.off)
+		if got := temporalEF(day).Cel.Slug; got != c.slug {
+			t.Errorf("Easter%+d (%s): slug = %q, want %q -- Passion week and Holy Week "+
+				"must not share a slug", c.off, day.Format("2006-01-02"), got, c.slug)
+		}
+	}
+}