Calculate the number of business days between two dates?

Question

In C#, how can I calculate the number of business (or weekdays) days between two dates?

Answer 1

I used the following code to also take in to account bank holidays:

public class WorkingDays
{
    public List GetHolidays()
    {
        var client = new WebClient();
        var json = client.DownloadString("https://www.gov.uk/bank-holidays.json");
        var js = new JavaScriptSerializer();
        var holidays = js.Deserialize >(json);
        return holidays["england-and-wales"].events.Select(d => d.date).ToList();
    }

    public int GetWorkingDays(DateTime from, DateTime to)
    {
        var totalDays = 0;
        var holidays = GetHolidays();
        for (var date = from.AddDays(1); date <= to; date = date.AddDays(1))
        {
            if (date.DayOfWeek != DayOfWeek.Saturday
                && date.DayOfWeek != DayOfWeek.Sunday
                && !holidays.Contains(date))
                totalDays++;
        }

        return totalDays;
    }
}

public class Holidays
{
    public string division { get; set; }
    public List events { get; set; }
}

public class Event
{
    public DateTime date { get; set; }
    public string notes { get; set; }
    public string title { get; set; }
}

And Unit Tests:

[TestClass]
public class WorkingDays
{
    [TestMethod]
    public void SameDayIsZero()
    {
        var service = new WorkingDays();

        var from = new DateTime(2013, 8, 12);

        Assert.AreEqual(0, service.GetWorkingDays(from, from));

    }

    [TestMethod]
    public void CalculateDaysInWorkingWeek()
    {
        var service = new WorkingDays();

        var from = new DateTime(2013, 8, 12);
        var to = new DateTime(2013, 8, 16);

        Assert.AreEqual(4, service.GetWorkingDays(from, to), "Mon - Fri = 4");

        Assert.AreEqual(1, service.GetWorkingDays(from, new DateTime(2013, 8, 13)), "Mon - Tues = 1");
    }

    [TestMethod]
    public void NotIncludeWeekends()
    {
        var service = new WorkingDays();

        var from = new DateTime(2013, 8, 9);
        var to = new DateTime(2013, 8, 16);

        Assert.AreEqual(5, service.GetWorkingDays(from, to), "Fri - Fri = 5");

        Assert.AreEqual(2, service.GetWorkingDays(from, new DateTime(2013, 8, 13)), "Fri - Tues = 2");
        Assert.AreEqual(1, service.GetWorkingDays(from, new DateTime(2013, 8, 12)), "Fri - Mon = 1");
    }

    [TestMethod]
    public void AccountForHolidays()
    {
        var service = new WorkingDays();

        var from = new DateTime(2013, 8, 23);

        Assert.AreEqual(0, service.GetWorkingDays(from, new DateTime(2013, 8, 26)), "Fri - Mon = 0");

        Assert.AreEqual(1, service.GetWorkingDays(from, new DateTime(2013, 8, 27)), "Fri - Tues = 1");
    }
}