Time and date functions in c#

I have been used to work with the COleDateTime objects in Visual Studio 98. There is a similar solution in C#?. Yes. The DateTime and TimeSpan Object. There are very similar to the useful COleDateTime and COleDateTimeSpan objects.

Here is a sample program that I have made to test the zeller´s congruence algorithm to determine the day of week from the Date. I have tested it from now until the 2100.


/* Zeller's Congruence to determine day of week */
int get_dayofweek(int date)
{
int d = date % 100;
int m = (date % 10000) / 100;
int y = date / 10000;
if (m < 3)
{
m = m + 12 ;
y = y - 1;
}
return ((2 + d + (13*m-2)/5 + y + y/4 - y/100 + y/400) % 7);
}


private void TestDayOfWeekAlgo()
{
DateTime t=new DateTime(2005,1,1,12,0,0);
TimeSpan i=new TimeSpan(1,0,0,0);
do
{
t+=i;
if ((int)t.DayOfWeek!=get_dayofweek(t.Year*10000+t.Month*100+t.Day))
{
MessageBox.Show("The day of week algorithm is not working correctly","Error",
MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
} while(t.Year<2100);
}

If you have time, you can read the ISO 8601 document about standard dates, and also some interesting things as about how to number the differents weeks of the year.