Studio711

Four Weeks Of February

This year, the month of February has 28 days and the month starts on a Sunday. That means that the four weeks of February fit perfectly onto four lines of the calendar assuming the calendar starts with Sunday.

That got me thinking about how rare this is. I wrote a quick program to figure it out:

for (int i = 2009; i >= DateTime.MinValue.Year; i–)

    if (new DateTime(i, 2, 1).DayOfWeek == DayOfWeek.Sunday)
    { 
        if (!new GregorianCalendar().IsLeapYear(i))
        {
            Console.WriteLine(i.ToString());
        }
    }
}

It turns out this is quite common. The last three times it happened were in 1998, 1987 and 1981. Looking back over the last 2000 years, it happens roughly once every nine years. The next occurrence will be in 2015.