DateTimeProvider and friends

DateTimeProvider.cs

	public abstract class DateTimeProvider
	{
		public static DateTimeProvider Current = new DefaultDateTimeProvider();
		public abstract DateTime UtcNow { get; }
	}

	public class DefaultDateTimeProvider : DateTimeProvider
	{
		public override DateTime UtcNow
		{
			get { return DateTime.UtcNow; }
		}
	}

MockDateTimeContext.cs

	public class MockDateTimeContext : IDisposable
	{
		public MockDateTimeContext(DateTime dateTime)
		{
			DateTimeProvider.Current = new MockDateTimeProvider(dateTime);
		}

		public void Dispose()
		{
			DateTimeProvider.Current = new DefaultDateTimeProvider();
		}
	}

MockDateTimeProvider.cs

	public class MockDateTimeProvider : DateTimeProvider
	{
		private readonly DateTime dateTime;

		public MockDateTimeProvider(DateTime dateTime)
		{
			this.dateTime = dateTime;
		}

		public override DateTime UtcNow
		{
			get { return dateTime.ToUniversalTime(); }
		}
	}