Example:
private void make(int year, int quarter)
{
DateTime starting, ending;
int month = (4 + 3 * (quarter - 1)) % 12;
starting = new DateTime(year, month, 1);
ending = starting.AddMonths(3).AddDays(-1);
MessageBox.Show(starting.ToString() + "," + ending.ToString());
}
make(2010, 1);
make(2010, 2);
make(2010, 3);
make(2010, 4);