using System;

public class Test
{
public static int Weekday(DateTime dt, DayOfWeek startOfWeek)
{
    return (dt.DayOfWeek - startOfWeek + 7) % 7;
}


	public static void Main()
	{
	DateTime value = new DateTime(2012, 8, 20);
	DayOfWeek weekday = (DayOfWeek)Weekday(value, DateTime.Now.DayOfWeek);

	Console.Write("normally:{0} changed to:{1}",value.DayOfWeek, weekday);	
	}
}