TimeService for .NET with ability to change Now/UtcNow/Today for testing purposes

TimeService.cs

using Microsoft.Win32;
using System;

namespace GarageTools
{
    /// <summary>
    /// Mocks DateTime Now/UtcNow/Today properties and allows setting them 
    /// (stores time shift in registry).
    /// </summary>
    /// <remarks>
    /// IMPORTANT: Add read/write permissions to all users of your application to 
    /// HKEY_USERS\.DEFAULT\Software\TimeService.
    /// </remarks>
    public static class TimeService
    {
#if DEBUG
        private const string ValueKey = "MyApp1Shift";
        private static readonly RegistryKey RegistryKey;

        static TimeService()
        {
            // create this subkey manually and set permissions if it fails
            RegistryKey = Registry.Users.CreateSubKey(".DEFAULT\\Software\\TimeService");
        }

        public static DateTime Now
        {
            get { return DateTime.Now + TimeShift; }
            set { TimeShift = value - DateTime.Now; }
        }

        public static DateTime Today
        {
            get { return Now.Date; }
        }

        public static DateTime UtcNow
        {
            get { return DateTime.UtcNow + TimeShift; }
            set { TimeShift = value - DateTime.UtcNow; }
        }

        public static TimeSpan TimeShift
        {
            get
            {
                var minutes = (string)RegistryKey.GetValue(ValueKey);
                return minutes == null ? TimeSpan.Zero : TimeSpan.FromMinutes(double.Parse(minutes));
            }
            set { RegistryKey.SetValue(ValueKey, value.TotalMinutes); }
        }

        public static void Reset()
        {
            TimeShift = TimeSpan.Zero;
        }
#else
        public static DateTime Now
        {
            get { return DateTime.Now; }
        }

        public static DateTime Today
        {
            get { return DateTime.Today; }
        }

        public static DateTime UtcNow
        {
            get { return DateTime.UtcNow; }
        }
#endif
    }
}