Question

I’m trying to find all quarters between 2 given dates.

For example if the current date is today(15 Jan 2013) and a date in the past is 01 Jan 2012, I should be getting the following result:
Dec 2012
Sep 2012
June 2012
March 2012

I can kind of keep deducting 3 months from the current date, but that is not going to be accurate as the test below denotes:

  [TestMethod]
        public void FindAllQuaters_FromAGivenDate_TillAPastDate()
        {
            var dateFinder = new FindQuarter();
            //Between Feb 2013 & Jan 2012
            var dates = dateFinder.GetAllQuarters(new DateTime(2013, 02, 01), new DateTime(2012, 01, 01)).ToList();

            Assert.IsTrue(dates.Count == 4);
            Assert.IsTrue(dates.First().Month == 12);
            Assert.IsTrue(dates.First().Year == 2012);

            Assert.IsTrue(dates.Skip(1).First().Month == 9);
            Assert.IsTrue(dates.Skip(1).First().Year == 2012);

            Assert.IsTrue(dates.Skip(2).First().Month == 6);
            Assert.IsTrue(dates.Skip(2).First().Year == 2012);

            Assert.IsTrue(dates.Skip(3).First().Month == 3);
            Assert.IsTrue(dates.Skip(3).First().Year == 2012);
        }
    }

    public class FindQuarter
    {
        public IEnumerable<DateTime> GetAllQuarters(DateTime current, DateTime past)
        {
            while (current > past)
            {
                current = current.AddMonths(-3);
                yield return current;
            }
        }
    }

How can I achieve this? The quarters are defined as March,June,September & December. I would also need the last date of that month(which I hope would be quick).

EDIT: This is not working because it keeps deducting 3 months from a given date, for example if the current date is feb 2013 and I reduce 3 months,I get Nov 2012 and not December 2012.

• Any dates in Jan,Feb,March will belong to first quarter i.e March

• Any dates in April,May,June will belong to second quarter i.e June

• Any dates in July,Aug,Sep will belong to third quarter i.e September

• Any dates in Oct,Nov,Dec will belong to fourth quarter i.e December

Answer 1

This seems to work.

        public IEnumerable<DateTime> GetAllQuarters(DateTime current, DateTime past)
        {
            var curQ = (int)Math.Ceiling(current.Month / 3.0M);
            var lastQEndDate = new DateTime(current.Year, curQ * 3, 1).AddMonths(-2).AddDays(-1);

            do
            {
                yield return lastQEndDate;
                lastQEndDate = lastQEndDate.AddMonths(-3);
            } while (lastQEndDate > past);
        }