Nearest completed quarter

Question

Is there a C# function which will give me the last day of the most recently finished Quarter given a date?

For example,

var lastDayOfLastQuarter = SomeFunction(jan 3, 2010);

would set lastDayOfLastQuarter = Dec 31, 2009

Answer 1

A simple function can calculate the last days of the most recently completed month:

public static DateTime LastQuarter(DateTime date)
{
    return new DateTime(date.Year, date.Month - ((date.Month - 1) % 3), 1).AddDays(-1);
}