See the clock and high frequency timer resolution of your PC from .NET

Program.cs

using System;
using System.Diagnostics;
using System.Threading;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Press any key to start, press SPACEBAR to pause, press ENTER to end");

            Console.ReadKey();

            var pauseMre = new ManualResetEventSlim(false);
            var endMre = new ManualResetEventSlim();
            // 0 = running, 1 = paused, 2 = stopped
            long state = 0;
            var lastTime = DateTime.UtcNow;
            var stopwatch = new Stopwatch();
            stopwatch.Start();

            ThreadPool.QueueUserWorkItem(_ =>
            {
                while (true)
                {
                    var currentState = Interlocked.Read(ref state);
                    if (currentState == 1)
                    {
                        Console.WriteLine();
                        Console.WriteLine("Paused, press any key to continue...");
                        Console.WriteLine();
                        
                        pauseMre.Wait();

                        lastTime = DateTime.UtcNow;
                        stopwatch.Restart();
                    }
                    else if (currentState == 2)
                    {
                        endMre.Set();
                        return;
                    }

                    var currentTime = DateTime.UtcNow;
                    var clockDiff = currentTime - lastTime;
                    var swDiff = stopwatch.Elapsed;

                    if (clockDiff.TotalMilliseconds > 0)
                    {
                        Console.Write("CLOCK CHANGED!     ");
                    }

                    Console.WriteLine("Clock diff: {0}ms", clockDiff.TotalMilliseconds);

                    if (swDiff.TotalMilliseconds > 0)
                    {
                        Console.Write("STOPWATCH CHANGED! ");
                    }

                    Console.WriteLine("Stopwatch diff: {0}ms", swDiff.TotalMilliseconds);

                    lastTime = currentTime;
                    stopwatch.Restart();
                }
            });

            while (true)
            {
                var key = Console.ReadKey();

                if (key.Key == ConsoleKey.Spacebar)
                {
                    // Pause
                    pauseMre.Reset();
                    Interlocked.Exchange(ref state, 1);
                    Console.ReadKey();
                    Interlocked.Exchange(ref state, 0);
                    pauseMre.Set();
                }
                else if (key.Key == ConsoleKey.Enter)
                {
                    // End
                    Interlocked.Exchange(ref state, 2);
                    endMre.Wait();
                    Console.WriteLine();
                    Console.WriteLine("Cancelled");
                    Console.WriteLine();
                    return;
                }
            }
        }
    }
}