diff --git a/LoopFollow/Stats/AggregatedStatsView.swift b/LoopFollow/Stats/AggregatedStatsView.swift
index 35dfeb29d..951e0b230 100644
--- a/LoopFollow/Stats/AggregatedStatsView.swift
+++ b/LoopFollow/Stats/AggregatedStatsView.swift
@@ -24,14 +24,9 @@ struct AggregatedStatsView: View {
         _showGMI = State(initialValue: Storage.shared.showGMI.value)
         _showStdDev = State(initialValue: Storage.shared.showStdDev.value)
 
-        let calendar = dateTimeUtils.displayCalendar()
-        let startOfToday = calendar.startOfDay(for: Date())
-        let end = calendar.date(byAdding: .second, value: -1, to: startOfToday) ?? Date()
-        let endDay = calendar.startOfDay(for: end)
-        let startDay = calendar.date(byAdding: .day, value: -7, to: endDay) ?? endDay
-        let start = calendar.startOfDay(for: startDay)
-        _startDate = State(initialValue: start)
-        _endDate = State(initialValue: end)
+        let range = StatsDateRange.lastComplete(days: 7)
+        _startDate = State(initialValue: range.start)
+        _endDate = State(initialValue: range.end)
     }
 
     var body: some View {
diff --git a/LoopFollow/Stats/AggregatedStatsViewModel.swift b/LoopFollow/Stats/AggregatedStatsViewModel.swift
index 005de2f41..253352e48 100644
--- a/LoopFollow/Stats/AggregatedStatsViewModel.swift
+++ b/LoopFollow/Stats/AggregatedStatsViewModel.swift
@@ -39,9 +39,8 @@ class AggregatedStatsViewModel: ObservableObject {
     }
 
     func updatePeriod(_ days: Int, completion: @escaping () -> Void = {}) {
-        let endDate = Date()
-        let startDate = dateTimeUtils.displayCalendar().date(byAdding: .day, value: -days, to: endDate) ?? endDate
-        updateDateRange(start: startDate, end: endDate, completion: completion)
+        let range = StatsDateRange.lastComplete(days: days)
+        updateDateRange(start: range.start, end: range.end, completion: completion)
     }
 
     func updateDateRange(start: Date, end: Date, completion: @escaping () -> Void = {}) {
diff --git a/LoopFollow/Stats/DateRangePicker.swift b/LoopFollow/Stats/DateRangePicker.swift
index 5bc9c334f..8b15e10d1 100644
--- a/LoopFollow/Stats/DateRangePicker.swift
+++ b/LoopFollow/Stats/DateRangePicker.swift
@@ -31,13 +31,13 @@ struct DateRangePicker: View {
 
     private var dayCount: Int {
         let calendar = dateTimeUtils.displayCalendar()
-        return calendar.dateComponents([.day], from: startDate, to: endDate).day ?? 0
+        let startDay = calendar.startOfDay(for: startDate)
+        let endDay = calendar.startOfDay(for: endDate)
+        return (calendar.dateComponents([.day], from: startDay, to: endDay).day ?? 0) + 1
     }
 
     private var lastFullDay: Date {
-        let calendar = dateTimeUtils.displayCalendar()
-        let startOfToday = calendar.startOfDay(for: Date())
-        return calendar.date(byAdding: .second, value: -1, to: startOfToday) ?? Date()
+        StatsDateRange.lastComplete(days: 1).end
     }
 
     var body: some View {
@@ -238,11 +238,9 @@ struct DateRangePicker: View {
     }
 
     private func setDateRange(days: Int) {
-        let calendar = dateTimeUtils.displayCalendar()
-        endDate = lastFullDay
-        let endDayStart = calendar.startOfDay(for: endDate)
-        let startDayStart = calendar.date(byAdding: .day, value: -days, to: endDayStart) ?? endDayStart
-        startDate = calendar.startOfDay(for: startDayStart)
+        let range = StatsDateRange.lastComplete(days: days)
+        startDate = range.start
+        endDate = range.end
         showStartDatePicker = false
         showEndDatePicker = false
         onDateChange()
diff --git a/LoopFollow/Stats/SimpleStatsViewModel.swift b/LoopFollow/Stats/SimpleStatsViewModel.swift
index 960e17c57..a3b97f1d1 100644
--- a/LoopFollow/Stats/SimpleStatsViewModel.swift
+++ b/LoopFollow/Stats/SimpleStatsViewModel.swift
@@ -66,7 +66,7 @@ class SimpleStatsViewModel: ObservableObject {
         let smbTotal = smbInPeriod.reduce(0.0) { $0 + $1.value }
         let totalBolusInPeriod = bolusTotal + smbTotal
 
-        let cutoffTime = Date().timeIntervalSince1970 - (Double(dataService.daysToAnalyze) * 24 * 60 * 60)
+        let cutoffTime = dataService.startDate.timeIntervalSince1970
         let allBolusDates = (bolusesInPeriod + smbInPeriod).map { $0.date }.filter { $0 >= cutoffTime }
         let actualDays = calculateActualDaysCovered(dates: allBolusDates, requestedDays: dataService.daysToAnalyze)
 
@@ -93,7 +93,7 @@ class SimpleStatsViewModel: ObservableObject {
 
         let totalCarbsInPeriod = dailyCarbs.values.reduce(0.0, +)
 
-        let daysWithData = max(dailyCarbs.count, 1)
+        let daysWithData = dataService.daysToAnalyze
 
         if daysWithData > 0 {
             avgCarbs = totalCarbsInPeriod / Double(daysWithData)
@@ -295,7 +295,7 @@ class SimpleStatsViewModel: ObservableObject {
         guard !dates.isEmpty else { return requestedDays }
 
         let calendar = dateTimeUtils.displayCalendar()
-        let cutoffTime = Date().timeIntervalSince1970 - (Double(requestedDays) * 24 * 60 * 60)
+        let cutoffTime = dataService.startDate.timeIntervalSince1970
         let filteredDates = dates.filter { $0 >= cutoffTime }
 
         var uniqueDays = Set<Date>()
diff --git a/LoopFollow/Stats/StatsDataService.swift b/LoopFollow/Stats/StatsDataService.swift
index 80ea66b54..4aa5b7c7f 100644
--- a/LoopFollow/Stats/StatsDataService.swift
+++ b/LoopFollow/Stats/StatsDataService.swift
@@ -32,9 +32,11 @@ class StatsDataService {
     func updateDateRange(start: Date, end: Date) {
         startDate = start
         endDate = end
-        // Also update daysToAnalyze for compatibility with existing code
-        let daysBetween = dateTimeUtils.displayCalendar().dateComponents([.day], from: start, to: end).day ?? 14
-        daysToAnalyze = max(daysBetween, 1)
+        let calendar = dateTimeUtils.displayCalendar()
+        let startDay = calendar.startOfDay(for: start)
+        let endDay = calendar.startOfDay(for: end)
+        let daysBetween = calendar.dateComponents([.day], from: startDay, to: endDay).day ?? 13
+        daysToAnalyze = daysBetween + 1
     }
 
     func ensureDataAvailable(onProgress: @escaping () -> Void, completion: @escaping () -> Void) {
diff --git a/LoopFollow/Stats/StatsDateRange.swift b/LoopFollow/Stats/StatsDateRange.swift
new file mode 100644
index 000000000..e2e00458b
--- /dev/null
+++ b/LoopFollow/Stats/StatsDateRange.swift
@@ -0,0 +1,17 @@
+// LoopFollow
+// StatsDateRange.swift
+
+import Foundation
+
+enum StatsDateRange {
+    /// Returns start/end dates for the last complete N-day period.
+    /// End is 23:59:59 of yesterday; start is 00:00:00 of the day N days back.
+    static func lastComplete(days: Int) -> (start: Date, end: Date) {
+        let calendar = dateTimeUtils.displayCalendar()
+        let startOfToday = calendar.startOfDay(for: Date())
+        let end = calendar.date(byAdding: .second, value: -1, to: startOfToday) ?? Date()
+        let endDayStart = calendar.startOfDay(for: end)
+        let start = calendar.date(byAdding: .day, value: -(days - 1), to: endDayStart) ?? endDayStart
+        return (start: calendar.startOfDay(for: start), end: end)
+    }
+}