MakeItTear.cs

using System;
using System.Linq;
using System.Threading;

namespace TearDateTime
{
    class Program
    {
        const int ITERATIONS = 20000;
        const int MAX_THREADS = 30;
        
        static int threads = 1; // 2x
        static int rerun = 0;

        static bool found = false;
        static bool stop = false; 

        static DateTime _value;
        static DateTime[] _values;

        static CountdownEvent _threadsEndend;

        static void Setup()
        {
            var range = Enumerable.Range(0, threads);
            var random = new Random();

            _values = range.Select(c => new DateTime((long)random.Next() << 30 | (long)random.Next())).ToArray();
            _threadsEndend = new CountdownEvent(threads * 2);

            _value = _values[0]; // Remove to get false positives! You will get 'normal' races, not tears.
        }

        static void Assign(int i)
        {
            for (int c = 0; c < ITERATIONS; c++)
            {
                _value = _values[i];
            }

            _threadsEndend.Signal();
        }

        static void FindTear()
        {
            for (int c = 0; c < ITERATIONS; c++)
            {
                var date = _value;
                if (!_values.Contains(date))
                {
                    Console.WriteLine($"Teared: {date}");
                    found = true;
                }
            }

            _threadsEndend.Signal();
        }

        static unsafe void Run()
        {
            while (!found && !stop)
            {
                Setup();

                Console.Clear();
                Console.WriteLine("----- Trying to tear ------");
                Console.WriteLine($"Running: {sizeof(IntPtr) * 8}bits");
                Console.WriteLine($"DateTime: {sizeof(DateTime) * 8}bits");
                Console.WriteLine($"Threads: {threads}");
                Console.WriteLine($"Rerun: {rerun}");
                Console.WriteLine();
                Console.WriteLine("---------- Values ----------");

                for (int i = 0; i < threads; i++)
                {
                    Console.WriteLine($"{i}: {_values[i]}");
                }

                Console.WriteLine();
                Console.WriteLine("---------- Tears ----------");


                for (int i = 0; i < threads; i++)
                {
                    var l = i;
                    new Thread(() => Assign(l)).Start();
                    new Thread(FindTear).Start();
                }

                _threadsEndend.Wait();
                _threadsEndend.Dispose();

                threads++;

                if (threads == MAX_THREADS)
                {
                    rerun++;
                    threads = 1;
                }
            }
        }

        static void Main(string[] args)
        {
            new Thread(Run).Start();
            Console.ReadLine();
            stop = true;
        }
    }
}