Question

I feel like this is math problem more than anything. My company has employees all over the country. Some parts of the company are on an “odd” pay cycle and some are on “even”. I call the starting date of a given pay period a “payperiod”. I need to do two things:

1) determine the payperiod in which a given date falls

//Something like this:
public static DateTime getPayPeriodStartDate(DateTime givenDate, string EvenOrOdd)
{ .. }

2) get a list of payperiods between two dates:

//Something like this:
public static List<DateTime> getPayPeriodsBetween(DateTime start, DateTime end, string EvenOrOdd)
{ .. }

I’m using a couple dates as fixed standards on which to base any future pay period dates. The fixed standard dates for even and odd are as follows:

• Even – 01/04/09
• Odd – 01/11/09

Each pay period starts on the sunday of the week and goes for two weeks. For instance, using the standard dates above, the first even pay period starts on 01/04/09 and ends on 01/17/09. The first odd pay period starts on 01/11/09 and ends on 01/24/09. As you can see, there is some overlap. We have thousands of employees so it’s necessary to split them up a bit.

I have a solution that is based on week numbers but it’s clunky and has to be “fixed” every new year. I’m wondering how you would handle this.

Answer 1

Not fully optimized or tested, but this is what I came up with:

const int DaysInPeriod = 14;

static IEnumerable<DateTime> GetPayPeriodsInRange(DateTime start, DateTime end, bool isOdd)
{
    var epoch = isOdd ? new DateTime(2009, 11, 1) : new DateTime(2009, 4, 1);
    var periodsTilStart = Math.Floor(((start - epoch).TotalDays) / DaysInPeriod);

    var next = epoch.AddDays(periodsTilStart * DaysInPeriod);

    if (next < start) next = next.AddDays(DaysInPeriod);

    while (next <= end)
    {
        yield return next;
        next = next.AddDays(DaysInPeriod);
    }

    yield break;
}

static DateTime GetPayPeriodStartDate(DateTime givenDate, bool isOdd)
{
    var candidatePeriods = GetPayPeriodsInRange(givenDate.AddDays(-DaysInPeriod), givenDate.AddDays(DaysInPeriod), isOdd);
    var period = from p in candidatePeriods where (p <= givenDate) && (givenDate < p.AddDays(DaysInPeriod)) select p;
    return period.First();
}