diff --git a/LoopFollow/Charts/BGChartModel.swift b/LoopFollow/Charts/BGChartModel.swift
index 9b451ac6a..27cb003ee 100644
--- a/LoopFollow/Charts/BGChartModel.swift
+++ b/LoopFollow/Charts/BGChartModel.swift
@@ -157,6 +157,7 @@ final class BGChartModel: ObservableObject {
     @Published var now: Date = .init()
     @Published var diaMarkers: [Date] = []
     @Published var midnightMarkers: [Date] = []
+    @Published var priorDayTimeMarkers: [Date] = []
     @Published var thirtyMinMark: Date? = nil
     @Published var ninetyMinMark: Date? = nil
 
@@ -596,6 +597,17 @@ final class BGChartModel: ObservableObject {
             }
             return cal
         }()
+
+        // Mark the current local time on each prior day. Calendar arithmetic
+        // preserves the displayed time of day across daylight-saving changes.
+        var priorDayTimes: [Date] = []
+        var priorDayTime = calendar.date(byAdding: .day, value: -1, to: currentNow)
+        while let marker = priorDayTime, marker > domainStart {
+            priorDayTimes.append(marker)
+            priorDayTime = calendar.date(byAdding: .day, value: -1, to: marker)
+        }
+        priorDayTimeMarkers = priorDayTimes
+
         var cursor = calendar.startOfDay(for: domainStart)
         while cursor <= domainEnd {
             if cursor >= domainStart {
diff --git a/LoopFollow/Charts/BGChartView.swift b/LoopFollow/Charts/BGChartView.swift
index 9098bd123..a28aaef65 100644
--- a/LoopFollow/Charts/BGChartView.swift
+++ b/LoopFollow/Charts/BGChartView.swift
@@ -1095,6 +1095,7 @@ private struct BGChartCanvas: View, Equatable {
             if showTreatments {
                 treatmentMarks
             }
+            priorDayTimeRuleMarks
             if !isSmall {
                 ruleMarks
             } else if model.showMidnight {
@@ -1462,6 +1463,15 @@ private struct BGChartCanvas: View, Equatable {
         }
     }
 
+    @ChartContentBuilder
+    private var priorDayTimeRuleMarks: some ChartContent {
+        ForEach(model.priorDayTimeMarkers.filter { $0 >= windowStart && $0 <= windowEnd }, id: \.self) { d in
+            RuleMark(x: .value("same time on prior day", d))
+                .lineStyle(StrokeStyle(lineWidth: 1, dash: isSmall ? [2, 2] : [2, 5]))
+                .foregroundStyle(Color.orange.opacity(isSmall ? 1 : 0.5))
+        }
+    }
+
     @ChartContentBuilder
     private var ruleMarks: some ChartContent {
         RuleMark(y: .value("low", model.lowLine))