using System;

public class Test
{
	public static void Main()
	{
		{
			Extensions.EnableKindFix = false;
		    var now = DateTime.Now.RoundToNearest(TimeSpan.FromMinutes(1));
		    Console.WriteLine(now + " --- " + now.Kind);
		    var nowFT = now.ToFileTimeUtc();
		    var nowDT = DateTime.FromFileTime(nowFT);
		    Console.WriteLine(nowDT);
		}
		{
			Extensions.EnableKindFix = true;
		    var now = DateTime.Now.RoundToNearest(TimeSpan.FromMinutes(1));
		    Console.WriteLine(now + " --- " + now.Kind);
		    var nowFT = now.ToFileTimeUtc();
		    var nowDT = DateTime.FromFileTime(nowFT);
		    Console.WriteLine(nowDT);
		}
	}
}
 
static class Extensions
{
    public static bool EnableKindFix { get; set; }
 
    public static DateTime RoundUp(this DateTime dt, TimeSpan d)
    {
        var delta = (d.Ticks - (dt.Ticks % d.Ticks)) % d.Ticks;
        return EnableKindFix
            ? new DateTime(dt.Ticks + delta, dt.Kind)
            : new DateTime(dt.Ticks + delta);
    }
 
    public static DateTime RoundDown(this DateTime dt, TimeSpan d)
    {
        var delta = dt.Ticks % d.Ticks;
        return EnableKindFix
            ? new DateTime(dt.Ticks - delta, dt.Kind)
            : new DateTime(dt.Ticks - delta);
    }
 
    public static DateTime RoundToNearest(this DateTime dt, TimeSpan d)
    {
        var delta = dt.Ticks % d.Ticks;
        bool roundUp = delta > d.Ticks / 2;
 
        return roundUp ? dt.RoundUp(d) : dt.RoundDown(d);
    }
}