using System;

public class Program

{

    public static void Main()

    {

        var a = Convert.ToDouble("1601510400000");

        var b = "18446681938112751616";

        var c = Convert.ToDouble(b);

        var d = "0001-01-01T00:00:00";

        var e = new Date(Convert.ToDateTime(d));

        var f = ((UInt64)((Date)e).ToDateTime.Subtract(new DateTime(1970, 1, 1)).TotalMilliseconds).ToString();

​

        Console.WriteLine(new DateTime(1970, 1, 1).AddMilliseconds(a));

        Console.WriteLine(new DateTime(1970, 1, 1));

        Console.WriteLine(DateTime.MinValue);

        Console.WriteLine(f);

    }

}

​

  public class Date : IComparable<Date>

  {

​

    public Date(DateTime date)

    {

      Month = date.Month;

      Year = date.Year;

      Day = date.Day;

    }

​

    public Date(int year, int month, int day)

    {

      Month = month;

      Year = year;

      Day = day;

    }

​

    public Date(Date other)

    {

      Month = other.Month;

      Year = other.Year;

      Day = other.Day;

    }

​

    public Date()

    {

      Month = DateTime.MinValue.Month;

      Year = DateTime.MinValue.Year;

      Day = DateTime.MinValue.Day;

    }

​

    public int Month { get; set; }

​

    public int Year { get; set; }

​

    public int Day { get; set; }

​

    public string UrlEncoded

    {

      get { return ToDateTime.ToString("yyyy-MM-dd"); }

    }

​

​

    public int CompareTo(Date other)

    {

      return IsAfter(other) ? 1 : other.IsAfter(this) ? -1 : 0;

    }

​

    public override string ToString()

    {

        return Month + "/" + Day + "/" + Year;

    }

​

    public DateTime ToDateTime

    {

      get

      {

        var dateTime = default(DateTime);

        try

        {

          dateTime = new DateTime(Year, Month, Day);

        }

        catch (Exception ex)

        {

​

        }

​

        return dateTime;

      }

    }

​

    public bool IsNever()

    {

      return (Year == DateTime.MinValue.Year && Month == DateTime.MinValue.Month && Day == DateTime.MinValue.Day)

             || (Year == DateTime.MaxValue.Year && Month == DateTime.MaxValue.Month && Day == DateTime.MaxValue.Day);

    }

​

    protected bool Equals(Date other)

    {

      if (ReferenceEquals(null, other)) return false;

      if (ReferenceEquals(this, other)) return true;

      return other.Year == Year && other.Month == Month && other.Day == Day;

    }

​

    public override bool Equals(object obj)

    {

      if (ReferenceEquals(null, obj)) return false;

      if (ReferenceEquals(this, obj)) return true;

      return obj.GetType() == GetType() && Equals((Date)obj);

    }

​

    public bool IsAfter(Date other)

    {

      return this > other;

    }

​

    public bool IsOnOrAfter(Date other)

    {

      return this >= other;

    }

​

    public bool IsBefore(Date other)

    {

      return this < other;

    }

​

    public bool IsOnOrBefore(Date other)

    {

      return this <= other;

    }

​

    public int YearSpan(Date date)

    {

      var isAfter = date > this;

      var d1 = isAfter ? date : this;

      var d2 = isAfter ? this : date;

      var value = d1.Year - d2.Year;

​

      if (d1.Month < d2.Month || (d1.Month == d2.Month && d1.Day < d2.Day))

      {

        value--;

      }

​

      return value;

    }

​

    public static bool operator !=(Date d1, Date d2)

    {

      return ReferenceEquals(d1, null) ? !ReferenceEquals(d2, null) : !d1.Equals(d2);

    }

​

    public static bool operator <(Date d1, Date d2)

    {

      return d1.ToDateTime < d2.ToDateTime;

    }

​

    public static bool operator <=(Date d1, Date d2)

    {

      return d1.ToDateTime <= d2.ToDateTime;

    }

​

    public static bool operator ==(Date d1, Date d2)

    {

      return ReferenceEquals(d1, null) ? ReferenceEquals(d2, null) : d1.Equals(d2);

    }

​

    public static bool operator >(Date d1, Date d2)

    {

      return d1.ToDateTime > d2.ToDateTime;

    }

​

    public static bool operator >=(Date d1, Date d2)

    {

      return d1.ToDateTime >= d2.ToDateTime;

    }

​

    public override int GetHashCode()

    {

      var result = Month.GetHashCode() * Day.GetHashCode();

      result = (result * 397) ^ (Year.GetHashCode());

      return result;

    }

  }