Adding TimeZone

--HG--
branch : 1.x

src/Orchard.Tests/Orchard.Framework.Tests.csproj

@@ -278,6 +278,7 @@
     <Compile Include="Stubs\StubVirtualPathMonitor.cs" />
     <Compile Include="Stubs\StubCacheManager.cs" />
     <Compile Include="Stubs\StubWebSiteFolder.cs" />
+    <Compile Include="Time\TimeZoneSelectorTests.cs" />
     <Compile Include="UI\Resources\ResourceManagerTests.cs" />
     <Compile Include="UI\ShapeTests.cs" />
     <Compile Include="Utility\ContainerExtensions.cs" />

src/Orchard.Tests/Stubs/StubWorkContextAccessor.cs

@@ -77,6 +77,8 @@ namespace Orchard.Tests.Stubs {
                 }
 
                 public string BaseUrl { get; set;}
+
+                public string SiteTimeZone { get; set; }
             }
 
             public class StubUser : IUser {

src/Orchard.Tests/Time/TimeZoneSelectorTests.cs

@@ -0,0 +1,85 @@
+using System;
+using System.Web;
+using Autofac;
+using NUnit.Framework;
+using Orchard.Tests.Stubs;
+using Orchard.Time;
+
+namespace Orchard.Tests.Time {
+    [TestFixture]
+    public class TimeZoneProviderTests {
+        private IContainer _container;
+        private IWorkContextStateProvider _workContextStateProvider;
+        private TestTimeZoneSelector _timeZoneSelector;
+
+        [SetUp]
+        public void Init() {
+            var builder = new ContainerBuilder();
+            builder.RegisterInstance(_timeZoneSelector = new TestTimeZoneSelector()).As<ITimeZoneSelector>();
+            builder.RegisterType<CurrentTimeZoneWorkContext>().As<IWorkContextStateProvider>();
+            builder.RegisterType<FallbackTimeZoneSelector>().As<ITimeZoneSelector>();
+            builder.RegisterType<SiteTimeZoneSelector>().As<ITimeZoneSelector>();
+            builder.RegisterType<StubWorkContextAccessor>().As<IWorkContextAccessor>();
+            
+            _container = builder.Build();
+            _workContextStateProvider = _container.Resolve<IWorkContextStateProvider>();
+        }
+
+        [Test]
+        public void ShouldProvideCurrentTimeZoneOnly() {
+            _timeZoneSelector.TimeZone = null;
+            var timeZone = _workContextStateProvider.Get<TimeZoneInfo>("Foo");
+
+            Assert.That(timeZone, Is.Null);
+        }
+
+        [Test]
+        public void DefaultTimeZoneIsLocal() {
+            _timeZoneSelector.Priority = -200;
+            var timeZone = _workContextStateProvider.Get<TimeZoneInfo>("CurrentTimeZone");
+
+            Assert.That(timeZone(new StubWorkContext()), Is.EqualTo(TimeZoneInfo.Local));
+        }
+
+        [Test]
+        public void TimeZoneProviderReturnsTimeZoneFromSelector() {
+            _timeZoneSelector.Priority = 999;
+            _timeZoneSelector.TimeZone = TimeZoneInfo.Utc;
+            var timeZone = _workContextStateProvider.Get<TimeZoneInfo>("CurrentTimeZone");
+
+            Assert.That(timeZone(new StubWorkContext()), Is.EqualTo(TimeZoneInfo.Utc));
+        }
+
+    }
+
+    public class TestTimeZoneSelector : ITimeZoneSelector {
+        public TimeZoneInfo TimeZone { get; set; }
+        public int Priority { get; set; }
+
+        public TimeZoneSelectorResult GetTimeZone(HttpContextBase context) {
+            return new TimeZoneSelectorResult {
+                Priority = Priority, 
+                TimeZone= TimeZone
+            };
+        }
+    }
+
+    public class StubWorkContext : WorkContext {
+        public override T Resolve<T>() {
+            throw new NotImplementedException();
+        }
+
+        public override bool TryResolve<T>(out T service) {
+            throw new NotImplementedException();
+        }
+
+        public override T GetState<T>(string name) {
+            return default(T);
+        }
+
+        public override void SetState<T>(string name, T value) {
+            
+        }
+    }
+}
+

src/Orchard.Web/Core/Common/Shapes.cs

@@ -23,12 +23,12 @@ namespace Orchard.Core.Common {
         }
 
         [Shape]
-        public IHtmlString PublishedState(HtmlHelper html, DateTime createdDateTimeUtc, DateTime? publisheddateTimeUtc) {
+        public IHtmlString PublishedState(dynamic Display, DateTime createdDateTimeUtc, DateTime? publisheddateTimeUtc) {
             if (!publisheddateTimeUtc.HasValue) {
                 return T("Draft");
             }
 
-            return html.DateTime(createdDateTimeUtc);
+            return Display.DateTime(DateTimeUtc: createdDateTimeUtc);
         }
 
         [Shape]

src/Orchard.Web/Core/Settings/Drivers/SiteSettingsPartDriver.cs

@@ -1,4 +1,5 @@
-using System.Net;
+using System.Linq;
+using System.Net;
 using JetBrains.Annotations;
 using Orchard.ContentManagement;
 using Orchard.ContentManagement.Drivers;
@@ -44,7 +45,8 @@ namespace Orchard.Core.Settings.Drivers {
 
             var model = new SiteSettingsPartViewModel {
                 Site = site,
-                SiteCultures = _cultureManager.ListCultures()
+                SiteCultures = _cultureManager.ListCultures(),
+                TimeZones = TimeZoneInfo.GetSystemTimeZones()
             };
 
             return ContentShape("Parts_Settings_SiteSettingsPart",
@@ -55,7 +57,8 @@ namespace Orchard.Core.Settings.Drivers {
             var site = _siteService.GetSiteSettings().As<SiteSettingsPart>();
             var model = new SiteSettingsPartViewModel { 
                 Site = site,
-                SiteCultures = _cultureManager.ListCultures()
+                SiteCultures = _cultureManager.ListCultures(),
+                TimeZones = TimeZoneInfo.GetSystemTimeZones()
             };
 
             var previousBaseUrl = model.Site.BaseUrl;

src/Orchard.Web/Core/Settings/Migrations.cs

@@ -91,9 +91,16 @@ namespace Orchard.Core.Settings {
                     .Column<string>("SiteCulture")
                     .Column<string>("ResourceDebugMode", c => c.WithDefault("FromAppSetting"))
                     .Column<int>("PageSize")
+                    .Column<string>("SiteTimeZone")
                 );
 
-            return 1;
+            SchemaBuilder.CreateTable("SiteSettings2PartRecord",
+                table => table
+                    .ContentPartRecord()
+                    .Column<string>("BaseUrl", c => c.Unlimited())
+                );
+
+            return 3;
         }
 
         public int UpdateFrom1() {
@@ -105,5 +112,14 @@ namespace Orchard.Core.Settings {
 
             return 2;
         }
+
+        public int UpdateFrom2() {
+            SchemaBuilder.AlterTable("SiteSettingsPartRecord",
+                table => table
+                    .AddColumn<string>("SiteTimeZone")
+                );
+
+            return 3;
+        }
     }
 }

src/Orchard.Web/Core/Settings/Models/SiteSettingsPart.cs

@@ -1,4 +1,5 @@
-using System.ComponentModel.DataAnnotations;
+using System;
+using System.ComponentModel.DataAnnotations;
 using Orchard.ContentManagement;
 using Orchard.Data.Conventions;
 using Orchard.Settings;
@@ -45,6 +46,11 @@ namespace Orchard.Core.Settings.Models {
             set { Record.PageSize = value; }
         }
 
+        public string SiteTimeZone {
+            get { return Record.SiteTimeZone; }
+            set { Record.SiteTimeZone = value; }
+        }
+
         [StringLengthMax]
         public string BaseUrl {
             get {

src/Orchard.Web/Core/Settings/Models/SiteSettingsPartRecord.cs

@@ -1,4 +1,5 @@
-using Orchard.ContentManagement.Records;
+using System;
+using Orchard.ContentManagement.Records;
 using Orchard.Settings;
 
 namespace Orchard.Core.Settings.Models {
@@ -24,5 +25,7 @@ namespace Orchard.Core.Settings.Models {
         public virtual ResourceDebugMode ResourceDebugMode { get; set; }
 
         public virtual int PageSize { get; set; }
+
+        public virtual string SiteTimeZone { get; set; }
     }
 }

src/Orchard.Web/Core/Settings/Services/SiteService.cs

@@ -36,6 +36,7 @@ namespace Orchard.Core.Settings.Services {
                         item.Record.SiteSalt = Guid.NewGuid().ToString("N");
                         item.Record.SiteName = "My Orchard Project Application";
                         item.Record.PageTitleSeparator = " - ";
+                        item.Record.SiteTimeZone = TimeZoneInfo.Local.Id;
                     }).ContentItem;
                 }
 

src/Orchard.Web/Core/Settings/ViewModels/SiteSettingsPartViewModel.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Web.Mvc;
 using Orchard.Core.Settings.Models;
 using Orchard.Settings;
@@ -7,6 +8,7 @@ namespace Orchard.Core.Settings.ViewModels {
     public class SiteSettingsPartViewModel  {
         public SiteSettingsPart Site { get; set; }
         public IEnumerable<string> SiteCultures { get; set; }
+        public IEnumerable<TimeZoneInfo> TimeZones { get; set; }
 
         [HiddenInput(DisplayValue = false)]
         public int Id {
@@ -47,5 +49,10 @@ namespace Orchard.Core.Settings.ViewModels {
             get { return Site.BaseUrl; }
             set { Site.BaseUrl = value; }
         }
+
+        public string TimeZone {
+            get { return Site.SiteTimeZone; }
+            set { Site.SiteTimeZone = value; }
+        }
     }
 }

src/Orchard.Web/Core/Settings/Views/EditorTemplates/Parts.Settings.SiteSettingsPart.cshtml

@@ -26,6 +26,12 @@
         @Html.ValidationMessage("SiteCulture", "*")
         <p>@Html.ActionLink(T("Add or remove supported cultures for the site.").ToString(), "Culture")</p>
     </div>
+    <div>
+        <label for="TimeZone">@T("Default Time Zone")</label>
+        @Html.DropDownList("TimeZone", new[] { new SelectListItem { Text = T("Local to server").Text, Value = "" } }.Union(new SelectList(Model.TimeZones, "Id", "", Model.TimeZone)))
+        @Html.ValidationMessage("TimeZone", "*")
+        <span class="hint">@T("Determines the default time zone which will should be used to display date and times.")</span>
+    </div>
     <div>
         <label for="PageTitleSeparator">@T("Page title separator")</label>
         @Html.EditorFor(x => x.PageTitleSeparator)

src/Orchard.Web/Core/Shapes/DateTimeShapes.cs

@@ -7,22 +7,27 @@ using Orchard.Mvc.Html;
 using Orchard.Services;
 
 namespace Orchard.Core.Shapes {
-    public class DateTimeShapes : ISingletonDependency {
+    public class DateTimeShapes : IDependency {
         private readonly IClock _clock;
+        private readonly IWorkContextAccessor _workContextAccessor;
 
-        public DateTimeShapes(IClock clock) {
+        public DateTimeShapes(
+            IClock clock,
+            IWorkContextAccessor workContextAccessor
+            ) {
             _clock = clock;
+            _workContextAccessor = workContextAccessor;
             T = NullLocalizer.Instance;
         }
 
         public Localizer T { get; set; }
 
         [Shape]
-        public IHtmlString DateTimeRelative(HtmlHelper Html, DateTime dateTimeUtc) {
+        public IHtmlString DateTimeRelative(dynamic Display, DateTime dateTimeUtc) {
             var time = _clock.UtcNow - dateTimeUtc;
 
             if (time.TotalDays > 7)
-                return Html.DateTime(dateTimeUtc.ToLocalTime(), T("'on' MMM d yyyy 'at' h:mm tt"));
+                return Display.DateTime(DateTimeUtc: dateTimeUtc, CustomFormat: T("'on' MMM d yyyy 'at' h:mm tt"));
             if (time.TotalHours > 24)
                 return T.Plural("1 day ago", "{0} days ago", time.Days);
             if (time.TotalMinutes > 60)
@@ -34,5 +39,30 @@ namespace Orchard.Core.Shapes {
 
             return T("a moment ago");
         }
+
+        [Shape]
+        public IHtmlString DateTime(DateTime DateTimeUtc, LocalizedString CustomFormat) {
+            //using a LocalizedString forces the caller to use a localizable format
+
+            if (CustomFormat == null || String.IsNullOrWhiteSpace(CustomFormat.Text)) {
+                return DateTime(DateTimeUtc, T("MMM d yyyy h:mm tt"));
+            }
+
+            return new MvcHtmlString(ConvertToDisplayTime(DateTimeUtc).ToString(CustomFormat.Text));
+        }
+
+        /// <summary>
+        /// Converts a Coordinated Universal Time (UTC) to the time in the current time zone.
+        /// </summary>
+        /// <param name="dateTimeUtc">The Coordinated Universal Time (UTC).</param>
+        /// <returns>The date and time in the selected time zone. Its System.DateTime.Kind property is System.DateTimeKind.Utc if the current zone is System.TimeZoneInfo.Utc; otherwise, its System.DateTime.Kind property is System.DateTimeKind.Unspecified.</returns>
+        private DateTime ConvertToDisplayTime(DateTime dateTimeUtc) {
+
+            // get the time zone for the current request
+            var timeZone = _workContextAccessor.GetContext().CurrentTimeZone;
+
+            return TimeZoneInfo.ConvertTimeFromUtc(dateTimeUtc, timeZone);
+        }
+
     }
 }

src/Orchard.Web/Modules/Orchard.ArchiveLater/Views/Parts/ArchiveLater.Metadata.SummaryAdmin.cshtml

@@ -4,7 +4,7 @@
 <ul class="pageStatus">
     <li>
         <img class="icon" src="@Href("~/Modules/Orchard.ArchiveLater/Content/Admin/images/scheduled.gif")" alt="@T("Scheduled")" title="@T("The page is scheduled for archiving")" />@T("Unpublish on")
-        @Html.DateTime((DateTime)Model.ScheduledArchiveUtc.ToLocalTime(), T("M/d/yyyy h:mm tt"))
+        @Display.DateTime(DateTimeUtc: (DateTime)Model.ScheduledArchiveUtc.ToLocalTime(), CustomFormat: T("M/d/yyyy h:mm tt"))
         &nbsp;&#124;&nbsp;
     </li>
 </ul>

src/Orchard.Web/Modules/Orchard.Comments/Views/Admin/Details.cshtml

@@ -83,7 +83,7 @@
                     @text
                 } 
                 </td>
-                <td>@Html.DateTime(commentEntry.Comment.CommentDateUtc.GetValueOrDefault())</td>
+                <td>@Display.DateTime(DateTimeUtc: commentEntry.Comment.CommentDateUtc.GetValueOrDefault())</td>
                 <td>
                     <ul class="actions">
                         <li class="construct">

src/Orchard.Web/Modules/Orchard.Comments/Views/Admin/Index.cshtml

@@ -77,7 +77,7 @@
                 </td>
                 <td>
                     @* would ideally have permalinks for individual comments *@
-                    <p><a href="@Url.ItemDisplayUrl(commentEntry.CommentedOn)#comments"><time>@Html.DateTime(commentEntry.Comment.CommentDateUtc.GetValueOrDefault())</time></a></p>
+                    <p><a href="@Url.ItemDisplayUrl(commentEntry.CommentedOn)#comments"><time>@Display.DateTime(DateTimeUtc: commentEntry.Comment.CommentDateUtc.GetValueOrDefault())</time></a></p>
                     @if (commentEntry.Comment.CommentText != null) {
                         var ellipsized = Html.Ellipsize(commentEntry.Comment.CommentText, 500);
                         var paragraphed = new HtmlString(ellipsized.ToHtmlString().Replace("\r\n", "</p><p>"));

src/Orchard.Web/Modules/Orchard.PublishLater/Views/Parts/PublishLater.Metadata.SummaryAdmin.cshtml

@@ -30,7 +30,7 @@
         }
         else {
             <img class="icon" src="@Href("~/Modules/Orchard.PublishLater/Content/Admin/images/scheduled.gif")" alt="@T("Scheduled")" title="@T("The page is scheduled for publishing")" /><text>  @T("Scheduled") </text>
-            @Html.DateTime(((DateTime?)Model.ScheduledPublishUtc).Value.ToLocalTime(), T("M/d/yyyy h:mm tt"))
+            @Display.DateTime(((DateTime?)Model.ScheduledPublishUtc).Value.ToLocalTime(), T("M/d/yyyy h:mm tt"))
         }&nbsp;&#124;&nbsp;</li>
     }
 </ul>

src/Orchard.Web/Modules/Orchard.Setup/SetupMode.cs

@@ -188,6 +188,10 @@ namespace Orchard.Setup {
             public string BaseUrl {
                 get { return ""; }
             }
+
+            public string SiteTimeZone {
+                get { return TimeZoneInfo.Local.Id; }
+             }        
         }
     }
 }

src/Orchard/Mvc/Html/HtmlHelperExtensions.cs

@@ -165,28 +165,6 @@ namespace Orchard.Mvc.Html {
 
         #endregion
 
-        #region Format Date/Time
-
-        public static LocalizedString DateTime(this HtmlHelper htmlHelper, DateTime? value, LocalizedString defaultIfNull) {
-            return value.HasValue ? htmlHelper.DateTime(value.Value) : defaultIfNull;
-        }
-
-        public static LocalizedString DateTime(this HtmlHelper htmlHelper, DateTime? value, LocalizedString defaultIfNull, LocalizedString customFormat) {
-            return value.HasValue ? htmlHelper.DateTime(value.Value, customFormat) : defaultIfNull;
-        }
-
-        public static LocalizedString DateTime(this HtmlHelper htmlHelper, DateTime value) {
-            //TODO: (erikpo) This default format should come from a site setting
-            return htmlHelper.DateTime(value.ToLocalTime(), new LocalizedString("MMM d yyyy h:mm tt")); //todo: above comment and get rid of just wrapping this as a localized string
-        }
-
-        public static LocalizedString DateTime(this HtmlHelper htmlHelper, DateTime value, LocalizedString customFormat) {
-            //TODO: (erikpo) In the future, convert this to "local" time before calling ToString
-            return new LocalizedString(value.ToString(customFormat.Text));
-        }
-
-        #endregion
-
         #region Image
 
         public static MvcHtmlString Image(this HtmlHelper htmlHelper, string src, string alt, object htmlAttributes) {

src/Orchard/Orchard.Framework.csproj

@@ -276,10 +276,16 @@
     <Compile Include="Security\IEncryptionService.cs" />
     <Compile Include="Security\CurrentUserWorkContext.cs" />
     <Compile Include="Security\Providers\DefaultEncryptionService.cs" />
+    <Compile Include="Services\Clock.cs" />
     <Compile Include="Settings\CurrentSiteWorkContext.cs" />
     <Compile Include="Settings\ResourceDebugMode.cs" />
     <Compile Include="Themes\CurrentThemeWorkContext.cs" />
     <Compile Include="Themes\ThemeManager.cs" />
+    <Compile Include="Time\CurrentTimeZoneWorkContext.cs" />
+    <Compile Include="Time\FallbackTimeZoneSelector.cs" />
+    <Compile Include="Time\ITimeZoneSelector.cs" />
+    <Compile Include="Time\SiteTimeZoneSelector.cs" />
+    <Compile Include="Time\TimeZoneSelectorResult.cs" />
     <Compile Include="UI\FlatPositionComparer.cs" />
     <Compile Include="UI\Navigation\Pager.cs" />
     <Compile Include="UI\Navigation\PagerParameters.cs" />
@@ -884,7 +890,7 @@
     <Compile Include="Security\Permissions\IPermissionProvider.cs" />
     <Compile Include="Security\Permissions\Permission.cs" />
     <Compile Include="Security\Providers\OrchardRoleProvider.cs" />
-    <Compile Include="Services\Clock.cs" />
+    <Compile Include="Services\IClock.cs" />
     <Compile Include="FileSystems\Media\IStorageFile.cs" />
     <Compile Include="FileSystems\Media\IStorageFolder.cs" />
     <Compile Include="FileSystems\Media\IStorageProvider.cs" />

src/Orchard/Services/Clock.cs

@@ -2,20 +2,6 @@
 using Orchard.Caching;
 
 namespace Orchard.Services {
-    public interface IClock : IVolatileProvider {
-        DateTime UtcNow { get; }
-
-        /// <summary>
-        /// Each retrieved value is cached during the specified amount of time.
-        /// </summary>
-        IVolatileToken When(TimeSpan duration);
-
-        /// <summary>
-        /// The cache is active until the specified time. Each subsequent access won't be cached.
-        /// </summary>
-        IVolatileToken WhenUtc(DateTime absoluteUtc);
-    }
-
     public class Clock : IClock {
         public DateTime UtcNow {
             get { return DateTime.UtcNow; }

src/Orchard/Services/IClock.cs

@@ -0,0 +1,56 @@
+using System;
+using Orchard.Caching;
+
+namespace Orchard.Services {
+    /// <summary>
+    /// Provides the current Utc <see cref="DateTime"/>, and time related method for cache management.
+    /// This service should be used whenever the current date and time are needed, instead of <seealso cref="DateTime"/> directly.
+    /// It also makes implementations more testable, as time can be mocked.
+    /// </summary>
+    public interface IClock : IVolatileProvider {
+        /// <summary>
+        /// Gets the current <see cref="DateTime"/> of the system, expressed in Utc
+        /// </summary>
+        DateTime UtcNow { get; }
+
+        /// <summary>
+        /// Provides a <see cref="IVolatileToken"/> instance which can be used to cache some information for a 
+        /// specific duration.
+        /// </summary>
+        /// <param name="duration">The duration that the token must be valid.</param>
+        /// <example>
+        /// This sample shows how to use the <see cref="When"/> method by returning the result of
+        /// a method named LoadVotes(), which is computed every 10 minutes only.
+        /// <code>
+        /// _cacheManager.Get("votes",
+        ///     ctx => {
+        ///         ctx.Monitor(_clock.When(TimeSpan.FromMinutes(10)));
+        ///         return LoadVotes();
+        /// });
+        /// </code>
+        /// </example>
+        IVolatileToken When(TimeSpan duration);
+
+        /// <summary>
+        /// Provides a <see cref="IVolatileToken"/> instance which can be used to cache some 
+        /// until a specific date and time.
+        /// </summary>
+        /// <param name="absoluteUtc">The date and time that the token must be valid until.</param>
+        /// <example>
+        /// This sample shows how to use the <see cref="WhenUtc"/> method by returning the result of
+        /// a method named LoadVotes(), which is computed once, and no more until the end of the year.
+        /// <code>
+        /// var endOfYear = _clock.UtcNow;
+        /// endOfYear.Month = 12;
+        /// endOfYear.Day = 31;
+        /// 
+        /// _cacheManager.Get("votes",
+        ///     ctx => {
+        ///         ctx.Monitor(_clock.WhenUtc(endOfYear));
+        ///         return LoadVotes();
+        /// });
+        /// </code>
+        /// </example>
+        IVolatileToken WhenUtc(DateTime absoluteUtc);
+    }
+}

src/Orchard/Settings/ISite.cs

@@ -1,4 +1,5 @@
-using Orchard.ContentManagement;
+using System;
+using Orchard.ContentManagement;
 
 namespace Orchard.Settings {
     /// <summary>
@@ -14,5 +15,6 @@ namespace Orchard.Settings {
         ResourceDebugMode ResourceDebugMode { get; set; }
         int PageSize { get; set; }
         string BaseUrl { get; }
+        string SiteTimeZone { get; }
     }
 }

src/Orchard/Time/CurrentTimeZoneWorkContext.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web;
+
+namespace Orchard.Time {
+    public class CurrentTimeZoneWorkContext : IWorkContextStateProvider {
+        private readonly IEnumerable<ITimeZoneSelector> _timeZoneSelectors;
+
+        public CurrentTimeZoneWorkContext(IEnumerable<ITimeZoneSelector> timeZoneSelectors) {
+            _timeZoneSelectors = timeZoneSelectors;
+        }
+
+        public Func<WorkContext, T> Get<T>(string name) {
+            if (name == "CurrentTimeZone") {
+                return ctx => (T)(object)CurrentTimeZone(ctx.HttpContext);
+            }
+            return null;
+        }
+
+        TimeZoneInfo CurrentTimeZone(HttpContextBase httpContext) {
+            var timeZone = _timeZoneSelectors
+                .Select(x => x.GetTimeZone(httpContext))
+                .Where(x => x != null)
+                .OrderByDescending(x => x.Priority)
+                .FirstOrDefault();
+
+            if (timeZone == null) {
+                return null;
+            }
+
+            return timeZone.TimeZone;
+        }
+    }
+}

src/Orchard/Time/FallbackTimeZoneSelector.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Web;
+
+namespace Orchard.Time {
+    /// <summary>
+    /// Implements <see cref="ITimeZoneSelector"/> by providing the timezone defined in the machine's local settings.
+    /// </summary>
+    public class FallbackTimeZoneSelector : ITimeZoneSelector {
+        public TimeZoneSelectorResult GetTimeZone(HttpContextBase context) {
+            return new TimeZoneSelectorResult {
+                Priority = -100,
+                TimeZone = TimeZoneInfo.Local
+            };
+        }
+    }
+}

src/Orchard/Time/ITimeZoneSelector.cs

@@ -0,0 +1,7 @@
+using System.Web;
+
+namespace Orchard.Time {
+    public interface ITimeZoneSelector : IDependency {
+        TimeZoneSelectorResult GetTimeZone(HttpContextBase context);
+    }
+}

src/Orchard/Time/SiteTimeZoneSelector.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Web;
+
+namespace Orchard.Time {
+    /// <summary>
+    /// Implements <see cref="ITimeZoneSelector"/> by providing the timezone defined in the sites settings.
+    /// </summary>
+    public class SiteTimeZoneSelector : ITimeZoneSelector {
+        private readonly IWorkContextAccessor _workContextAccessor;
+
+        public SiteTimeZoneSelector(IWorkContextAccessor workContextAccessor) {
+            _workContextAccessor = workContextAccessor;
+        }
+
+        public TimeZoneSelectorResult GetTimeZone(HttpContextBase context) {
+            var siteTimeZoneId = _workContextAccessor.GetContext(context).CurrentSite.SiteTimeZone;
+            
+            if (String.IsNullOrEmpty(siteTimeZoneId)) {
+                return null;
+            }
+
+            return new TimeZoneSelectorResult {
+                Priority = -5,
+                TimeZone = TimeZoneInfo.FindSystemTimeZoneById(siteTimeZoneId)
+            };
+        }
+    }
+}

src/Orchard/Time/TimeZoneSelectorResult.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace Orchard.Time {
+    public class TimeZoneSelectorResult {
+        public int Priority { get; set; }
+        public TimeZoneInfo TimeZone { get; set; }
+    }
+}

src/Orchard/WorkContext.cs

@@ -1,4 +1,5 @@
-using System.Web;
+using System;
+using System.Web;
 using Orchard.Environment.Extensions.Models;
 using Orchard.Security;
 using Orchard.Settings;
@@ -75,5 +76,13 @@ namespace Orchard {
             get { return GetState<string>("CurrentCulture"); }
             set { SetState("CurrentCulture", value); }
         }
+
+        /// <summary>
+        /// Time zone of the work context
+        /// </summary>
+        public TimeZoneInfo CurrentTimeZone {
+            get { return GetState<TimeZoneInfo>("CurrentTimeZone"); }
+            set { SetState("CurrentTimeZone", value); }
+        }
     }
 }