Replace max sleep hours with earliest reasonable bedtime

Bedtime/Bedtime/ContentView.swift

@@ -51,10 +51,9 @@ struct ContentView: View {
     private var bedtimeRecommendation: BedtimeRecommendation {
         ViewModel.generateBedtimeRecommendation(
             wakeTime: userPreferences.wakeTime,
+            earliestBedtime: userPreferences.earliestReasonableBedtime,
             sleepGoal: userPreferences.sleepGoalHours,
-            sleepBank: sleepBank,
-            maxSleepHours: userPreferences.maxSleepHoursPerNight,
-            minSleepHours: userPreferences.minSleepHoursPerNight
+            sleepBank: sleepBank
         )
     }
 

Bedtime/Bedtime/Models/UserPreferences.swift

@@ -14,21 +14,24 @@ final class UserPreferences {
     var wakeTime: Date
     var sleepBankDays: Int
     var lastUpdated: Date
-    var maxSleepHoursPerNight: Double
-    var minSleepHoursPerNight: Double
-
+    var earliestReasonableBedtime: Date
+
     init(
         sleepGoalHours: Double = 8.0,
         wakeTime: Date = Calendar.current.date(from: DateComponents(hour: 7, minute: 0)) ?? Date(),
         sleepBankDays: Int = 7,
-        maxSleepHoursPerNight: Double = 10,
-        minSleepHoursPerNight: Double = 5
+        earliestReasonableBedtime: Date = Calendar.current.date(from: DateComponents(hour: 21, minute: 0)) ?? Date()
     ) {
         self.sleepGoalHours = sleepGoalHours
         self.wakeTime = wakeTime
         self.sleepBankDays = sleepBankDays
         self.lastUpdated = Date()
-        self.maxSleepHoursPerNight = maxSleepHoursPerNight
-        self.minSleepHoursPerNight = minSleepHoursPerNight
+        self.earliestReasonableBedtime = earliestReasonableBedtime
+    }
+
+    /// Convenience accessor for the nominal sleep-window length from this
+    /// schedule's stored times. Now-aware/DST math lives in `SleepWindow`.
+    var nominalMaxSleepHours: Double {
+        SleepWindow.nominalWindowHours(earliestBedtime: earliestReasonableBedtime, wakeTime: wakeTime)
     }
 }

Bedtime/Bedtime/Models/ViewModel.swift

@@ -44,13 +44,19 @@ class ViewModel {
 
     static func generateBedtimeRecommendation(
         wakeTime: Date,
+        earliestBedtime: Date,
         sleepGoal: Double,
         sleepBank: SleepBank,
-        maxSleepHours: Double,
-        minSleepHours: Double
+        referenceDate: Date = Date()
     ) -> BedtimeRecommendation {
         let calendar = Calendar.current
-
+        let maxSleepHours = SleepWindow.maxSleepHours(
+            earliestBedtime: earliestBedtime,
+            wakeTime: wakeTime,
+            referenceDate: referenceDate,
+            calendar: calendar
+        )
+
         // Calculate how much sleep we need tonight
         // If we're in debt, we need extra sleep to catch up
         var totalSleepNeeded = sleepGoal - sleepBank.currentBalance
@@ -62,9 +68,6 @@ class ViewModel {
         } else if totalSleepNeeded > maxSleepHours {
             totalSleepNeeded = maxSleepHours
             reason = "You can't catch up in one night, so just get as much as possible."
-        } else if totalSleepNeeded < minSleepHours {
-            totalSleepNeeded = minSleepHours
-            reason = "You're way ahead!"
         } else if sleepBank.isInDebt {
             let debtHours = sleepBank.debtHours
             reason = "You need \(String(format: "%.1f", totalSleepNeeded)) hours tonight to catch up on your \(String(format: "%.1f", debtHours))-hour sleep debt."

Bedtime/Bedtime/Utils/SleepWindow.swift

@@ -0,0 +1,73 @@
+//
+//  SleepWindow.swift
+//  Bedtime
+//
+//  Created by Greg on 10/5/25.
+//
+
+import Foundation
+
+/// Pure time-interval math for the sleep window between an earliest reasonable
+/// bedtime and a wake time. Split into a now-aware (DST-adjusted) measure for the
+/// recommendation and a nominal wall-clock measure for schedule display.
+struct SleepWindow {
+    /// Real hours between the earliest reasonable bedtime and wake time for the
+    /// night ending at the next wake from `referenceDate`. Anchoring on the wake
+    /// (forward from now) then searching backward for the bedtime keeps the
+    /// window correct even when the app is opened mid-sleep, and lets `Calendar`
+    /// absorb the ±1h of a DST transition instead of assuming a 24h day.
+    static func maxSleepHours(
+        earliestBedtime: Date,
+        wakeTime: Date,
+        referenceDate: Date = Date(),
+        calendar: Calendar = .current
+    ) -> Double {
+        let wakeComponents = calendar.dateComponents([.hour, .minute], from: wakeTime)
+        let bedComponents = calendar.dateComponents([.hour, .minute], from: earliestBedtime)
+
+        guard
+            let wake = calendar.nextDate(
+                after: referenceDate,
+                matching: wakeComponents,
+                matchingPolicy: .strict
+            ),
+            let bed = calendar.nextDate(
+                after: wake,
+                matching: bedComponents,
+                matchingPolicy: .strict,
+                direction: .backward
+            )
+        else {
+            // Fall back to a nominal wall-clock window if a match can't be found.
+            return nominalWindowHours(earliestBedtime: earliestBedtime, wakeTime: wakeTime, calendar: calendar)
+        }
+
+        return wake.timeIntervalSince(bed) / 3600.0
+    }
+
+    /// Nominal wall-clock length of the sleep window (a stable 10h for a 9pm–7am
+    /// schedule, ignoring DST). For settings/schedule display, where a value that
+    /// wobbles ±1h twice a year would just be confusing.
+    static func nominalWindowHours(
+        earliestBedtime: Date,
+        wakeTime: Date,
+        calendar: Calendar = .current
+    ) -> Double {
+        let wakeMinutes = minutesSinceMidnight(wakeTime, calendar: calendar)
+        let earliestMinutes = minutesSinceMidnight(earliestBedtime, calendar: calendar)
+
+        let sleepMinutes: Int
+        if earliestMinutes >= wakeMinutes {
+            sleepMinutes = (24 * 60 - earliestMinutes) + wakeMinutes
+        } else {
+            sleepMinutes = wakeMinutes - earliestMinutes
+        }
+
+        return Double(sleepMinutes) / 60.0
+    }
+
+    private static func minutesSinceMidnight(_ date: Date, calendar: Calendar) -> Int {
+        let components = calendar.dateComponents([.hour, .minute], from: date)
+        return (components.hour ?? 0) * 60 + (components.minute ?? 0)
+    }
+}

Bedtime/Bedtime/Views/SettingsView.swift

@@ -28,6 +28,10 @@ struct SettingsView: View {
     @State private var debugMessage: String?
     #endif
 
+    private var earliestBedtimeBinding: Binding<Date> {
+        $preferences.earliestReasonableBedtime
+    }
+
     var body: some View {
         NavigationStack {
             Form {
@@ -76,31 +80,15 @@ struct SettingsView: View {
                 }
 
                 Section("Sleep Limits") {
-                    VStack(alignment: .leading, spacing: 8) {
-                        HStack {
-                            Text("Max sleep hours per night")
-                            Spacer()
-                            Text("\(String(format: "%.0f", preferences.maxSleepHoursPerNight)) hours")
-                                .foregroundColor(.secondary)
-                        }
-
-                        Slider(value: $preferences.maxSleepHoursPerNight, in: 8...16, step: 1) {
-                            Text("Max")
-                        }
-                        .accentColor(.blue)
-
-                        HStack {
-                            Text("Min sleep hours per night")
-                            Spacer()
-                            Text("\(String(format: "%.0f", preferences.minSleepHoursPerNight)) hours")
-                                .foregroundColor(.secondary)
-                        }
-
-                        Slider(value: $preferences.minSleepHoursPerNight, in: 2...10, step: 1) {
-                            Text("Min")
-                        }
-                        .accentColor(.blue)
-                    }
+                    DatePicker(
+                        "Earliest reasonable bedtime",
+                        selection: earliestBedtimeBinding,
+                        displayedComponents: .hourAndMinute
+                    )
+
+                    Text("Won't recommend sleeping before this time — allowing up to \(String(format: "%.1f", preferences.nominalMaxSleepHours)) hours per night based on your wake time (aside from DST adjustments).")
+                        .font(.caption)
+                        .foregroundColor(.secondary)
                 }
 
                 Section("Data Sources") {