diff --git a/tariff/fixed/zone.go b/tariff/fixed/zone.go
index 4b1dea8c4..7f68f1c03 100644
--- a/tariff/fixed/zone.go
+++ b/tariff/fixed/zone.go
@@ -47,10 +47,14 @@ func (r Zones) TimeTableMarkers() []HourMin {
 
 	for _, z := range r {
 		if !z.Hours.From.IsNil() {
-			res = append(res, z.Hours.From)
+			if !slices.Contains(res, z.Hours.From) {
+				res = append(res, z.Hours.From)
+			}
 		}
 		if !z.Hours.To.IsNil() {
-			res = append(res, z.Hours.To)
+			if !slices.Contains(res, z.Hours.To) {
+				res = append(res, z.Hours.To)
+			}
 		}
 	}
 
diff --git a/tariff/fixed/zone_test.go b/tariff/fixed/zone_test.go
index 867144132..72d325ea6 100644
--- a/tariff/fixed/zone_test.go
+++ b/tariff/fixed/zone_test.go
@@ -54,8 +54,12 @@ func TestZonesTimeTableMarkers(t *testing.T) {
 			To:   HourMin{2, 0},
 		}},
 		{Hours: TimeRange{
-			From: HourMin{3, 30},
-			To:   HourMin{4, 30},
+			From: HourMin{2, 0}, // make sure adjacent zones don't generate duplicate markers
+			To:   HourMin{3, 0},
+		}},
+		{Hours: TimeRange{
+			From: HourMin{4, 30},
+			To:   HourMin{5, 30},
 		}},
 	}
 
@@ -63,14 +67,15 @@ func TestZonesTimeTableMarkers(t *testing.T) {
 		{0, 0},
 		{1, 0},
 		{2, 0},
-		{3, 0}, // 1hr intervals
-		{3, 30},
+		{3, 0},
 		{4, 0}, // 1hr intervals
 		{4, 30},
+		{5, 0}, // 1hr intervals
+		{5, 30},
 	}
 
 	// 1hr intervals
-	for hour := 5; hour < 24; hour++ {
+	for hour := 6; hour < 24; hour++ {
 		expect = append(expect, HourMin{hour, 0})
 	}
 
diff --git a/tariff/fixed_test.go b/tariff/fixed_test.go
index cda0233ae..ae340855b 100644
--- a/tariff/fixed_test.go
+++ b/tariff/fixed_test.go
@@ -45,7 +45,7 @@ func TestFixedSplitZones(t *testing.T) {
 			Price float64
 			Hours string
 		}{
-			{0.1, "0-5:30,21-0"},
+			{0.1, "0-5:30,20-21,21-0"},
 		},
 	})
 	require.NoError(t, err)
@@ -80,8 +80,8 @@ func TestFixedSplitZones(t *testing.T) {
 			End:   dayStart.Add(6 * time.Hour),
 		})
 
-		// 06:00-21:00 0.5
-		for hour := 6; hour < 21; hour++ {
+		// 06:00-20:00 0.5
+		for hour := 6; hour < 20; hour++ {
 			expect = append(expect, api.Rate{
 				Value: 0.5,
 				Start: dayStart.Add(time.Hour * time.Duration(hour)),
@@ -89,8 +89,8 @@ func TestFixedSplitZones(t *testing.T) {
 			})
 		}
 
-		// 21:00-00:00 0.1
-		for hour := 21; hour < 24; hour++ {
+		// 20:00-21:00,21:00-00:00 0.1
+		for hour := 20; hour < 24; hour++ {
 			expect = append(expect, api.Rate{
 				Value: 0.1,
 				Start: dayStart.Add(time.Hour * time.Duration(hour)),