Make schedule time-zone behavior explicit

IPCamLapse.Tests/CaptureScheduleServiceTests.cs

@@ -5,7 +5,8 @@ namespace IPCamLapse.Tests;
 
 public sealed class CaptureScheduleServiceTests
 {
-    private readonly CaptureScheduleService _service = new();
+    private static readonly TimeZoneInfo TestZone = CreateTestZone();
+    private readonly CaptureScheduleService _service = new(TestZone);
 
     [Fact]
     public void FutureOneTimeScheduleWaitsForStart()
@@ -27,7 +28,7 @@ public void FutureOneTimeScheduleWaitsForStart()
     public void DailyWindowReportsNextLocalStart()
     {
         var localNow = new DateTime(2026, 8, 27, 18, 0, 0, DateTimeKind.Unspecified);
-        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TimeZoneInfo.Local);
+        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TestZone);
 
         var result = _service.GetAvailability(new CaptureSchedule
         {
@@ -37,15 +38,15 @@ public void DailyWindowReportsNextLocalStart()
         }, utcNow);
 
         Assert.False(result.Active);
-        var expected = TimeZoneInfo.ConvertTimeToUtc(localNow.Date.AddDays(1).AddHours(7), TimeZoneInfo.Local);
+        var expected = TimeZoneInfo.ConvertTimeToUtc(localNow.Date.AddDays(1).AddHours(7), TestZone);
         Assert.Equal(expected, result.NextStartUtc);
     }
 
     [Fact]
     public void OvernightDailyWindowIncludesEarlyMorning()
     {
         var localNow = new DateTime(2026, 8, 27, 2, 0, 0, DateTimeKind.Unspecified);
-        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TimeZoneInfo.Local);
+        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TestZone);
 
         var result = _service.GetAvailability(new CaptureSchedule
         {
@@ -61,7 +62,7 @@ public void OvernightDailyWindowIncludesEarlyMorning()
     public void WeeklyWindowReportsTheNextSelectedDay()
     {
         var localNow = new DateTime(2026, 8, 27, 12, 0, 0, DateTimeKind.Unspecified);
-        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TimeZoneInfo.Local);
+        var utcNow = TimeZoneInfo.ConvertTimeToUtc(localNow, TestZone);
 
         var result = _service.GetAvailability(new CaptureSchedule
         {
@@ -73,6 +74,121 @@ public void WeeklyWindowReportsTheNextSelectedDay()
 
         Assert.False(result.Active);
         var nextMonday = new DateTime(2026, 8, 31, 8, 0, 0, DateTimeKind.Unspecified);
-        Assert.Equal(TimeZoneInfo.ConvertTimeToUtc(nextMonday, TimeZoneInfo.Local), result.NextStartUtc);
+        Assert.Equal(TimeZoneInfo.ConvertTimeToUtc(nextMonday, TestZone), result.NextStartUtc);
+    }
+
+    [Fact]
+    public void SpringForwardWallTimeMovesForwardByTheDstGap()
+    {
+        var invalid = new DateTime(2026, 3, 8, 2, 30, 0, DateTimeKind.Unspecified);
+
+        var result = _service.ConvertWallTimeToUtc(invalid);
+
+        Assert.Equal(new DateTime(2026, 3, 8, 7, 30, 0, DateTimeKind.Utc), result);
+    }
+
+    [Fact]
+    public void AmbiguousOneTimeStartChoosesEarlierUtcOccurrence()
+    {
+        var repeated = new DateTime(2026, 11, 1, 1, 30, 0, DateTimeKind.Unspecified);
+
+        var result = _service.ConvertWallTimeToUtc(repeated);
+
+        Assert.Equal(new DateTime(2026, 11, 1, 5, 30, 0, DateTimeKind.Utc), result);
+    }
+
+    [Theory]
+    [InlineData(5)]
+    [InlineData(6)]
+    public void BothRepeatedHourInstantsAreInsideRecurringWindow(int utcHour)
+    {
+        var result = _service.GetAvailability(new CaptureSchedule
+        {
+            Frequency = ScheduleFrequency.Daily,
+            WindowStartLocal = TimeSpan.FromHours(1),
+            WindowEndLocal = TimeSpan.FromHours(2)
+        }, new DateTime(2026, 11, 1, utcHour, 30, 0, DateTimeKind.Utc));
+
+        Assert.True(result.Active);
+    }
+
+    [Fact]
+    public void SecondFallBackHourSelectsItsOwnFutureRecurringStart()
+    {
+        var result = _service.GetAvailability(new CaptureSchedule
+        {
+            Frequency = ScheduleFrequency.Daily,
+            WindowStartLocal = TimeSpan.FromHours(1.5),
+            WindowEndLocal = TimeSpan.FromHours(1.75)
+        }, new DateTime(2026, 11, 1, 6, 20, 0, DateTimeKind.Utc));
+
+        Assert.False(result.Active);
+        Assert.Equal(new DateTime(2026, 11, 1, 6, 30, 0, DateTimeKind.Utc), result.NextStartUtc);
+    }
+
+    [Theory]
+    [InlineData(ScheduleFrequency.Daily)]
+    [InlineData(ScheduleFrequency.Weekly)]
+    public void WindowStartingBeforeRepeatedHourIncludesSecondOccurrence(ScheduleFrequency frequency)
+    {
+        var result = _service.GetAvailability(new CaptureSchedule
+        {
+            Frequency = frequency,
+            WeeklyDay = DayOfWeek.Sunday,
+            WindowStartLocal = TimeSpan.FromMinutes(30),
+            WindowEndLocal = TimeSpan.FromHours(1.25)
+        }, new DateTime(2026, 11, 1, 6, 10, 0, DateTimeKind.Utc));
+
+        Assert.True(result.Active);
+    }
+
+    [Fact]
+    public void SpringForwardGapDoesNotActivateBeforeAdjustedStart()
+    {
+        var result = _service.GetAvailability(new CaptureSchedule
+        {
+            Frequency = ScheduleFrequency.Daily,
+            WindowStartLocal = TimeSpan.FromHours(2.5),
+            WindowEndLocal = TimeSpan.FromHours(4)
+        }, new DateTime(2026, 3, 8, 7, 10, 0, DateTimeKind.Utc));
+
+        Assert.False(result.Active);
+        Assert.Equal(new DateTime(2026, 3, 8, 7, 30, 0, DateTimeKind.Utc), result.NextStartUtc);
+    }
+
+    [Fact]
+    public void UtcZoneRemainsDeterministic()
+    {
+        var service = new CaptureScheduleService(TimeZoneInfo.Utc);
+        var wallTime = new DateTime(2026, 6, 1, 12, 15, 0, DateTimeKind.Unspecified);
+
+        Assert.Equal(
+            new DateTime(2026, 6, 1, 12, 15, 0, DateTimeKind.Utc),
+            service.ConvertWallTimeToUtc(wallTime));
+    }
+
+    private static TimeZoneInfo CreateTestZone()
+    {
+        var daylight = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(
+            new DateTime(2020, 1, 1),
+            new DateTime(2030, 12, 31),
+            TimeSpan.FromHours(1),
+            TimeZoneInfo.TransitionTime.CreateFloatingDateRule(
+                new DateTime(1, 1, 1, 2, 0, 0),
+                3,
+                2,
+                DayOfWeek.Sunday),
+            TimeZoneInfo.TransitionTime.CreateFloatingDateRule(
+                new DateTime(1, 1, 1, 2, 0, 0),
+                11,
+                1,
+                DayOfWeek.Sunday));
+        return TimeZoneInfo.CreateCustomTimeZone(
+            "IPCamLapse-Test-Eastern",
+            TimeSpan.FromHours(-5),
+            "Test Eastern",
+            "Test Standard",
+            "Test Daylight",
+            [daylight]);
     }
 }

IPCamLapse.Tests/TimeZonePageTests.cs

@@ -0,0 +1,63 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+namespace IPCamLapse.Tests;
+
+public sealed class TimeZonePageTests
+{
+    [Theory]
+    [InlineData("/Sessions/Create")]
+    [InlineData("/System")]
+    public async Task PagesShowInjectedStartupTimeZoneAndCurrentOffset(string path)
+    {
+        var zone = TimeZoneInfo.CreateCustomTimeZone(
+            "IPCamLapse-Test-Zone",
+            TimeSpan.FromHours(3),
+            "Test Zone",
+            "Test Zone");
+        var now = new DateTimeOffset(2026, 9, 8, 12, 0, 0, TimeSpan.Zero);
+        await using var factory = new TimeZoneFactory(zone, new FixedTimeProvider(now));
+        using var client = factory.CreateClient();
+
+        var response = await client.GetAsync(path);
+        response.EnsureSuccessStatusCode();
+        var html = await response.Content.ReadAsStringAsync();
+
+        Assert.Contains("IPCamLapse-Test-Zone", html, StringComparison.Ordinal);
+        Assert.Contains("UTC+03:00", html, StringComparison.Ordinal);
+    }
+
+    private sealed class TimeZoneFactory : WebApplicationFactory<Program>
+    {
+        private readonly TimeZoneInfo _timeZone;
+        private readonly TimeProvider _timeProvider;
+
+        public TimeZoneFactory(TimeZoneInfo timeZone, TimeProvider timeProvider)
+        {
+            _timeZone = timeZone;
+            _timeProvider = timeProvider;
+        }
+
+        protected override void ConfigureWebHost(IWebHostBuilder builder)
+        {
+            builder.ConfigureServices(services =>
+            {
+                services.RemoveAll<TimeZoneInfo>();
+                services.RemoveAll<TimeProvider>();
+                services.AddSingleton(_timeZone);
+                services.AddSingleton(_timeProvider);
+            });
+        }
+    }
+
+    private sealed class FixedTimeProvider : TimeProvider
+    {
+        private readonly DateTimeOffset _now;
+
+        public FixedTimeProvider(DateTimeOffset now) => _now = now;
+
+        public override DateTimeOffset GetUtcNow() => _now;
+    }
+}

IPCamLapse/Pages/Sessions/Create.cshtml

@@ -126,6 +126,7 @@
             <div class="card shadow-sm mb-4">
                 <div class="card-header"><h2 class="h5 mb-0"><span class="form-section-number">03</span>Schedule</h2></div>
                 <div class="card-body">
+                    <p class="small text-muted">Recurring windows use @Model.TimeZoneDisplay. Changing the host time zone requires an application restart.</p>
                     <div class="row g-3">
                         <div class="col-md-4">
                             <label asp-for="Session.Configuration.Schedule.Frequency" class="form-label fw-semibold">Frequency</label>

IPCamLapse/Pages/Sessions/Create.cshtml.cs

@@ -12,19 +12,28 @@ public sealed class CreateModel : PageModel
     private readonly ICameraUrlPolicy _cameraUrlPolicy;
     private readonly IStorageService _storage;
     private readonly IApplicationSettingsService _applicationSettings;
+    private readonly ICaptureScheduleService _schedule;
+    private readonly TimeProvider _timeProvider;
+    private readonly TimeZoneInfo _timeZone;
 
     public CreateModel(
         ICaptureSessionService sessions,
         ICameraProfileService profiles,
         ICameraUrlPolicy cameraUrlPolicy,
         IStorageService storage,
-        IApplicationSettingsService applicationSettings)
+        IApplicationSettingsService applicationSettings,
+        ICaptureScheduleService schedule,
+        TimeProvider timeProvider,
+        TimeZoneInfo timeZone)
     {
         _sessions = sessions;
         _profiles = profiles;
         _cameraUrlPolicy = cameraUrlPolicy;
         _storage = storage;
         _applicationSettings = applicationSettings;
+        _schedule = schedule;
+        _timeProvider = timeProvider;
+        _timeZone = timeZone;
     }
 
     [BindProperty]
@@ -37,6 +46,7 @@ public CreateModel(
     public IReadOnlyList<CameraProfile> Profiles { get; private set; } = Array.Empty<CameraProfile>();
     public StorageStatus Storage { get; private set; } = new(0, 1, 0, 0, false, null);
     public long EstimatedFrameBytes { get; private set; } = 350 * 1024;
+    public string TimeZoneDisplay => FormatTimeZone(_timeZone, _timeProvider.GetUtcNow());
 
     public async Task OnGetAsync()
     {
@@ -75,12 +85,10 @@ public async Task<IActionResult> OnPostAsync()
             Session.Configuration.AllowInvalidCertificate = false;
         }
         Session.Id = Guid.NewGuid().ToString("N")[..8];
-        Session.CreatedAt = DateTime.UtcNow;
+        Session.CreatedAt = _timeProvider.GetUtcNow().UtcDateTime;
         Session.Status = SessionStatus.Ready;
         Session.Configuration.Schedule.StartAtUtc = StartAtLocal.HasValue
-            ? TimeZoneInfo.ConvertTimeToUtc(
-                DateTime.SpecifyKind(StartAtLocal.Value, DateTimeKind.Unspecified),
-                TimeZoneInfo.Local)
+            ? _schedule.ConvertWallTimeToUtc(StartAtLocal.Value)
             : null;
         await _sessions.CreateSessionAsync(Session);
         return RedirectToPage("/Sessions/Details", new { id = Session.Id });
@@ -116,7 +124,8 @@ private void ValidateSchedule()
         var schedule = Session.Configuration.Schedule;
         if (schedule.Frequency == ScheduleFrequency.Once && !StartAtLocal.HasValue)
             ModelState.AddModelError(nameof(StartAtLocal), "Choose a start time.");
-        if (StartAtLocal.HasValue && StartAtLocal.Value <= DateTime.Now &&
+        if (StartAtLocal.HasValue &&
+            _schedule.ConvertWallTimeToUtc(StartAtLocal.Value) <= _timeProvider.GetUtcNow().UtcDateTime &&
             schedule.Frequency == ScheduleFrequency.Once)
         {
             ModelState.AddModelError(nameof(StartAtLocal), "Start time must be in the future.");
@@ -144,4 +153,11 @@ private async Task LoadPageDataAsync()
         Storage = await _storage.GetStatusAsync();
         EstimatedFrameBytes = _applicationSettings.Current.EstimatedFrameBytes;
     }
+
+    private static string FormatTimeZone(TimeZoneInfo timeZone, DateTimeOffset now)
+    {
+        var offset = timeZone.GetUtcOffset(now);
+        var sign = offset < TimeSpan.Zero ? "−" : "+";
+        return $"{timeZone.Id} (UTC{sign}{offset.Duration():hh\\:mm})";
+    }
 }

IPCamLapse/Pages/System.cshtml

@@ -21,6 +21,8 @@
     <span class="text-muted">@Model.Health.Checks.Count(check => check.Healthy) of @Model.Health.Checks.Count checks passed</span>
 </div>
 
+<p class="small text-muted mb-4">Active scheduling time zone: @Model.TimeZoneDisplay</p>
+
 <div class="card shadow-sm mb-4">
     <div class="card-body p-0">
         <div class="list-group list-group-flush">

IPCamLapse/Pages/System.cshtml.cs

@@ -8,15 +8,32 @@ public sealed class SystemModel : PageModel
 {
     private readonly ISystemHealthService _health;
     private readonly IStorageService _storage;
+    private readonly TimeProvider _timeProvider;
+    private readonly TimeZoneInfo _timeZone;
 
-    public SystemModel(ISystemHealthService health, IStorageService storage)
+    public SystemModel(
+        ISystemHealthService health,
+        IStorageService storage,
+        TimeProvider timeProvider,
+        TimeZoneInfo timeZone)
     {
         _health = health;
         _storage = storage;
+        _timeProvider = timeProvider;
+        _timeZone = timeZone;
     }
 
     public SystemHealthReport Health { get; private set; } = new(Array.Empty<HealthCheckItem>());
     public StorageStatus Storage { get; private set; } = new(0, 1, 0, 0, false, null);
+    public string TimeZoneDisplay
+    {
+        get
+        {
+            var offset = _timeZone.GetUtcOffset(_timeProvider.GetUtcNow());
+            var sign = offset < TimeSpan.Zero ? "−" : "+";
+            return $"{_timeZone.Id} (UTC{sign}{offset.Duration():hh\\:mm})";
+        }
+    }
 
     public async Task OnGetAsync()
     {

IPCamLapse/Program.cs

@@ -21,6 +21,7 @@
     IConfigureOptions<KeyManagementOptions>,
     DataProtectionKeyRingOptionsSetup>();
 builder.Services.AddSingleton(TimeProvider.System);
+builder.Services.AddSingleton<TimeZoneInfo>(_ => TimeZoneInfo.Local);
 
 builder.Services
     .AddOptions<LocalAccessOptions>()