diff --git a/internal/briefing/derived_daypart_summaries_module.go b/internal/briefing/derived_daypart_summaries_module.go
index 3e3223d..ef27344 100644
--- a/internal/briefing/derived_daypart_summaries_module.go
+++ b/internal/briefing/derived_daypart_summaries_module.go
@@ -400,7 +400,7 @@ func multipleSummaryDates(summaries []forecast.DailySummary) bool {
 }
 
 func daypartKey(daypart forecast.DaypartSummary, prefixDate bool) string {
-	key := normalizedKey(daypart.Name)
+	key := forecast.CanonicalDaypartKey(daypart.Name)
 	if key == "" {
 		key = "unnamed"
 	}
@@ -409,21 +409,3 @@ func daypartKey(daypart forecast.DaypartSummary, prefixDate bool) string {
 	}
 	return daypart.Period.Start.Format(timeutil.DateLayout) + "_" + key
 }
-
-func normalizedKey(value string) string {
-	lower := strings.ToLower(strings.TrimSpace(value))
-	var out strings.Builder
-	lastUnderscore := false
-	for _, r := range lower {
-		if unicode.IsLetter(r) || unicode.IsDigit(r) {
-			out.WriteRune(r)
-			lastUnderscore = false
-			continue
-		}
-		if !lastUnderscore {
-			out.WriteByte('_')
-			lastUnderscore = true
-		}
-	}
-	return strings.Trim(out.String(), "_")
-}
diff --git a/internal/forecast/dayparts.go b/internal/forecast/dayparts.go
index f9f981c..b017619 100644
--- a/internal/forecast/dayparts.go
+++ b/internal/forecast/dayparts.go
@@ -2,7 +2,9 @@ package forecast
 
 import (
 	"fmt"
+	"strings"
 	"time"
+	"unicode"
 
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/weatherdata"
@@ -14,6 +16,25 @@ type DaypartDefinition struct {
 	End   string `json:"end"`
 }
 
+// CanonicalDaypartKey returns the stable identity for a configured daypart name.
+func CanonicalDaypartKey(value string) string {
+	lower := strings.ToLower(strings.TrimSpace(value))
+	var out strings.Builder
+	lastUnderscore := false
+	for _, r := range lower {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) {
+			out.WriteRune(r)
+			lastUnderscore = false
+			continue
+		}
+		if !lastUnderscore {
+			out.WriteByte('_')
+			lastUnderscore = true
+		}
+	}
+	return strings.Trim(out.String(), "_")
+}
+
 type DaypartWindow struct {
 	Name   string          `json:"name"`
 	Start  time.Time       `json:"start"`
diff --git a/internal/forecast/derive_test.go b/internal/forecast/derive_test.go
index 433eb80..88519f4 100644
--- a/internal/forecast/derive_test.go
+++ b/internal/forecast/derive_test.go
@@ -658,3 +658,26 @@ func assertTimedValueClose(t *testing.T, name string, got *TimedValue, want floa
 		t.Fatalf("%s = %#v, want %v", name, got, want)
 	}
 }
+
+func TestCanonicalDaypartKey(t *testing.T) {
+	for _, tt := range []struct {
+		name  string
+		value string
+		want  string
+	}{
+		{name: "blank", value: " \t ", want: ""},
+		{name: "casing", value: "MORNING", want: "morning"},
+		{name: "punctuation runs", value: " Morning--Commute / School ", want: "morning_commute_school"},
+		{name: "Unicode", value: "Déjà Vu", want: "déjà_vu"},
+		{name: "letters and digits", value: "Day 1 Outlook", want: "day_1_outlook"},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := CanonicalDaypartKey(tt.value); got != tt.want {
+				t.Fatalf("CanonicalDaypartKey(%q) = %q, want %q", tt.value, got, tt.want)
+			}
+		})
+	}
+	if CanonicalDaypartKey("Morning commute") != CanonicalDaypartKey("MORNING--COMMUTE") {
+		t.Fatal("equivalent configured names must have the same canonical daypart key")
+	}
+}
diff --git a/internal/generatedtext/render_context.go b/internal/generatedtext/render_context.go
index c56d9c3..b9baa49 100644
--- a/internal/generatedtext/render_context.go
+++ b/internal/generatedtext/render_context.go
@@ -3,9 +3,7 @@ package generatedtext
 import (
 	"fmt"
 	"sort"
-	"strings"
 	"time"
-	"unicode"
 
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/briefing"
 	"gitea.maximumdirect.net/eric/weatherreporter/internal/facts"
@@ -698,7 +696,7 @@ func orderedDaypartRows(dayparts *map[string]briefing.DerivedDaypartSummaryModul
 }
 
 func daypartModuleKeyCandidates(daypart forecast.DaypartSummary) []string {
-	key := normalizedDaypartKey(daypart.Name)
+	key := forecast.CanonicalDaypartKey(daypart.Name)
 	if key == "" {
 		key = "unnamed"
 	}
@@ -708,24 +706,6 @@ func daypartModuleKeyCandidates(daypart forecast.DaypartSummary) []string {
 	return []string{key, daypart.Period.Start.Format(timeutil.DateLayout) + "_" + key}
 }
 
-func normalizedDaypartKey(value string) string {
-	lower := strings.ToLower(strings.TrimSpace(value))
-	var out strings.Builder
-	lastUnderscore := false
-	for _, r := range lower {
-		if unicode.IsLetter(r) || unicode.IsDigit(r) {
-			out.WriteRune(r)
-			lastUnderscore = false
-			continue
-		}
-		if !lastUnderscore {
-			out.WriteByte('_')
-			lastUnderscore = true
-		}
-	}
-	return strings.Trim(out.String(), "_")
-}
-
 func locationName(metadata briefing.Metadata) string {
 	if metadata.Location != nil {
 		if metadata.Location.Name != "" && metadata.Location.Region != "" {