diff --git a/src/EventHub.Domain/Events/Registrations/EventRegistrationManager.cs b/src/EventHub.Domain/Events/Registrations/EventRegistrationManager.cs
index 152cadc..85c34d2 100644
--- a/src/EventHub.Domain/Events/Registrations/EventRegistrationManager.cs
+++ b/src/EventHub.Domain/Events/Registrations/EventRegistrationManager.cs
@@ -1,17 +1,26 @@
 using System.Threading.Tasks;
 using Volo.Abp;
 using Volo.Abp.Domain.Services;
+using Volo.Abp.Guids;
 using Volo.Abp.Identity;
+using Volo.Abp.Timing;
 
 namespace EventHub.Events.Registrations
 {
-    public class EventRegistrationManager : DomainService
+    public class EventRegistrationManager : IDomainService
     {
         private readonly IEventRegistrationRepository _eventRegistrationRepository;
+        private readonly IGuidGenerator _guidGenerator;
+        private readonly IClock _clock;
 
-        public EventRegistrationManager(IEventRegistrationRepository eventRegistrationRepository)
+        public EventRegistrationManager(
+            IEventRegistrationRepository eventRegistrationRepository,
+            IGuidGenerator guidGenerator,
+            IClock clock)
         {
             _eventRegistrationRepository = eventRegistrationRepository;
+            _guidGenerator = guidGenerator;
+            _clock = clock;
         }
 
         public async Task RegisterAsync(
@@ -38,7 +47,7 @@ namespace EventHub.Events.Registrations
                 
             await _eventRegistrationRepository.InsertAsync(
                 new EventRegistration(
-                    GuidGenerator.Create(),
+                    _guidGenerator.Create(),
                     @event.Id,
                     user.Id
                 )
@@ -69,12 +78,7 @@ namespace EventHub.Events.Registrations
 
         public bool IsPastEvent(Event @event)
         {
-            if (Clock.Now > @event.EndTime)
-            {
-                return true;
-            }
-
-            return false;
+            return _clock.Now > @event.EndTime;
         }
     }
 }
diff --git a/test/EventHub.Domain.Tests/Events/Event_Tests.cs b/test/EventHub.Domain.Tests/Events/Event_Tests.cs
index 270adf0..6a49efd 100644
--- a/test/EventHub.Domain.Tests/Events/Event_Tests.cs
+++ b/test/EventHub.Domain.Tests/Events/Event_Tests.cs
@@ -21,6 +21,33 @@ namespace EventHub.Events
             );
         }
 
+        [Fact]
+        public void Should_Update_Event_Time()
+        {
+            // ARRANGE
+            var evnt = new Event(
+                Guid.NewGuid(),
+                Guid.NewGuid(),
+                "1a8j3v0d",
+                "Introduction to the ABP Framework",
+                DateTime.Now,
+                DateTime.Now.AddHours(2),
+                "In this event, we will introduce the ABP Framework..."
+            );
+
+            var newStartTime = DateTime.Now.AddHours(1);
+            var newEndTime = DateTime.Now.AddHours(2);
+
+            //ACT
+            evnt.SetTime(newStartTime, newEndTime);
+
+            //ASSERT
+            evnt.StartTime.ShouldBe(newStartTime);
+            evnt.EndTime.ShouldBe(newEndTime);
+            evnt.GetLocalEvents()
+                .ShouldContain(x => x.EventData is EventTimeChangingEventData);
+        }
+
         [Fact]
         public void Should_Not_Allow_End_Time_Earlier_Than_Start_Time()
         {
diff --git a/test/EventHub.Domain.Tests/Events/Registrations/EventRegistrationManager_UnitTests.cs b/test/EventHub.Domain.Tests/Events/Registrations/EventRegistrationManager_UnitTests.cs
new file mode 100644
index 0000000..2485287
--- /dev/null
+++ b/test/EventHub.Domain.Tests/Events/Registrations/EventRegistrationManager_UnitTests.cs
@@ -0,0 +1,73 @@
+using NSubstitute;
+using Shouldly;
+using System;
+using System.Threading.Tasks;
+using Volo.Abp.Guids;
+using Volo.Abp.Identity;
+using Volo.Abp.Timing;
+using Xunit;
+
+namespace EventHub.Events.Registrations
+{
+    public class EventRegistrationManager_UnitTests
+    {
+        [Fact]
+        public void IsPastEvent()
+        {
+            var clock = Substitute.For<IClock>();
+            clock.Now.Returns(DateTime.Now);
+
+            var registrationManager = new EventRegistrationManager(
+                null, null, clock
+            );
+
+            var evnt = new Event(
+                Guid.NewGuid(),
+                Guid.NewGuid(),
+                "1a8j3v0d",
+                "Introduction to the ABP Framework",
+                DateTime.Now.AddDays(-10), // Start time
+                DateTime.Now.AddDays(-9), // End time
+                "In this event, we will introduce the ABP Framework..."
+            );
+
+            registrationManager.IsPastEvent(evnt).ShouldBeTrue();
+        }
+
+        [Fact]
+        public async Task RegisterAsync()
+        {
+            var evnt = new Event(
+                Guid.NewGuid(),
+                Guid.NewGuid(),
+                "1a8j3v0d",
+                "Introduction to the ABP Framework",
+                DateTime.Now.AddDays(1),
+                DateTime.Now.AddDays(2),
+                "In this event, we will introduce the ABP Framework..."
+            );
+
+            var user = new IdentityUser(Guid.NewGuid(), "john", "john@abp.io");
+
+            var repository = Substitute.For<IEventRegistrationRepository>();
+            repository.ExistsAsync(evnt.Id, user.Id).Returns(Task.FromResult(false));
+
+            var guidGenerator = SimpleGuidGenerator.Instance;
+
+            var clock = Substitute.For<IClock>();
+            clock.Now.Returns(DateTime.Now);
+
+            var registrationManager = new EventRegistrationManager(
+                repository, guidGenerator, clock
+            );
+
+            await registrationManager.RegisterAsync(evnt, user);
+
+            await repository
+                .Received()
+                .InsertAsync(
+                    Arg.Is<EventRegistration>(er => er.EventId == evnt.Id && er.UserId == user.Id)
+            );
+        }
+    }
+}