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

Here is the function which we can use to calculate business days between two date. I'm not using holiday list as it can vary accross country/region.

If we want to use it anyway we can take third argument as list of holiday and before incrementing count we should check that list does not contains d

public static int GetBussinessDaysBetweenTwoDates(DateTime StartDate,   DateTime EndDate)
    {
        if (StartDate > EndDate)
            return -1;

        int bd = 0;

        for (DateTime d = StartDate; d < EndDate; d = d.AddDays(1))
        {
            if (d.DayOfWeek != DayOfWeek.Saturday && d.DayOfWeek != DayOfWeek.Sunday)
                bd++;
        }

        return bd;
    }

Answer 2

Here's some code for that purpose, with swedish holidays but you can adapt what holidays to count. Note that I added a limit you might want to remove, but it was for a web-based system and I didnt want anyone to enter some huge date to hog the process

  public static int GetWorkdays(DateTime from ,DateTime to)
    {
        int limit = 9999;
        int counter = 0;
        DateTime current = from;
        int result = 0;

        if (from > to)
        {
            DateTime temp = from;
            from = to;
            to = temp;
        }

        if (from >= to)
        {
            return 0;
        }


        while (current <= to && counter < limit)
        {
            if (IsSwedishWorkday(current))
            {
                result++;
            }
            current = current.AddDays(1);
            counter++;

        }
        return result;
    }


    public static bool IsSwedishWorkday(DateTime date)
    {
        return (!IsSwedishHoliday(date) && date.DayOfWeek != DayOfWeek.Saturday && date.DayOfWeek != DayOfWeek.Sunday);
    }

    public static bool IsSwedishHoliday(DateTime date)
    {
        return (
        IsSameDay(GetEpiphanyDay(date.Year), date) ||
        IsSameDay(GetMayDay(date.Year), date) ||
        IsSameDay(GetSwedishNationalDay(date.Year), date) ||
        IsSameDay(GetChristmasDay(date.Year), date) ||
        IsSameDay(GetBoxingDay(date.Year), date) ||
        IsSameDay(GetGoodFriday(date.Year), date) ||
        IsSameDay(GetAscensionDay(date.Year), date) ||
        IsSameDay(GetAllSaintsDay(date.Year), date) ||
        IsSameDay(GetMidsummersDay(date.Year), date) ||
        IsSameDay(GetPentecostDay(date.Year), date) ||
        IsSameDay(GetEasterMonday(date.Year), date) ||
        IsSameDay(GetNewYearsDay(date.Year), date) ||
        IsSameDay(GetEasterDay(date.Year), date)
        );
    }

    // Trettondagen
    public static DateTime GetEpiphanyDay(int year)
    {
        return new DateTime(year, 1, 6);
    }

    // Första maj
    public static DateTime GetMayDay(int year)
    {
        return new DateTime(year,5,1);
    }

    // Juldagen
    public static DateTime GetSwedishNationalDay(int year)
    {
        return new DateTime(year, 6, 6);
    }


    // Juldagen
    public static DateTime GetNewYearsDay(int year)
    {
        return new DateTime(year,1,1);
    }

    // Juldagen
    public static DateTime GetChristmasDay(int year)
    {
        return new DateTime(year,12,25);
    }

    // Annandag jul
    public static DateTime GetBoxingDay(int year)
    {
        return new DateTime(year, 12, 26);
    }


    // Långfredagen
    public static DateTime GetGoodFriday(int year)
    {
        return GetEasterDay(year).AddDays(-3);
    }

    // Kristi himmelsfärdsdag
    public static DateTime GetAscensionDay(int year)
    {
        return GetEasterDay(year).AddDays(5*7+4);
    }

    // Midsommar
    public static DateTime GetAllSaintsDay(int year)
    {
        DateTime result = new DateTime(year,10,31);
        while (result.DayOfWeek != DayOfWeek.Saturday)
        {
            result = result.AddDays(1);
        }
        return result;
    }

    // Midsommar
    public static DateTime GetMidsummersDay(int year)
    {
        DateTime result = new DateTime(year, 6, 20);
        while (result.DayOfWeek != DayOfWeek.Saturday)
        {
            result = result.AddDays(1);
        }
        return result;
    }

    // Pingstdagen
    public static DateTime GetPentecostDay(int year)
    {
        return GetEasterDay(year).AddDays(7 * 7);
    }

    // Annandag påsk
    public static DateTime GetEasterMonday(int year)
    {
        return GetEasterDay(year).AddDays(1);
    }
    public static DateTime GetEasterDay(int y)
    {
        double c;
        double n;
        double k;
        double i;
        double j;
        double l;
        double m;
        double d;
        c = System.Math.Floor(y / 100.0);
        n = y - 19 * System.Math.Floor(y / 19.0);
        k = System.Math.Floor((c - 17) / 25.0);
        i = c - System.Math.Floor(c / 4) - System.Math.Floor((c - k) / 3) + 19 * n + 15;
        i = i - 30 * System.Math.Floor(i / 30);
        i = i - System.Math.Floor(i / 28) * (1 - System.Math.Floor(i / 28) * System.Math.Floor(29 / (i + 1)) * System.Math.Floor((21 - n) / 11));
        j = y + System.Math.Floor(y / 4.0) + i + 2 - c + System.Math.Floor(c / 4);
        j = j - 7 * System.Math.Floor(j / 7);
        l = i - j;
        m = 3 + System.Math.Floor((l + 40) / 44);// month
        d = l + 28 - 31 * System.Math.Floor(m / 4);// day

        double days = ((m == 3) ? d : d + 31);

        DateTime result = new DateTime(y, 3, 1).AddDays(days-1);

        return result;
    }

Answer 3

    int BusinessDayDifference(DateTime Date1, DateTime Date2)
    {
        int Sign = 1;
        if (Date2 > Date1)
        {
            Sign = -1;
            DateTime TempDate = Date1;
            Date1 = Date2;
            Date2 = TempDate;
        }
        int BusDayDiff = (int)(Date1.Date - Date2.Date).TotalDays;
        if (Date1.DayOfWeek == DayOfWeek.Saturday)
            BusDayDiff -= 1;
        if (Date2.DayOfWeek == DayOfWeek.Sunday)
            BusDayDiff -= 1;
        int Week1 = GetWeekNum(Date1);
        int Week2 = GetWeekNum(Date2);
        int WeekDiff = Week1 - Week2;
        BusDayDiff -= WeekDiff * 2;
        foreach (DateTime Holiday in Holidays)
            if (Date1 >= Holiday && Date2 <= Holiday)
                BusDayDiff--;
        BusDayDiff *= Sign;
        return BusDayDiff;
    }

    private int GetWeekNum(DateTime Date)
    {
        return (int)(Date.AddDays(-(int)Date.DayOfWeek).Ticks / TimeSpan.TicksPerDay / 7);
    }

Answer 4

Here's yet another idea - this method allows to specify any working week and holidays.

The idea here is that we find the core of the date range from the first first working day of the week to the last weekend day of the week. This enables us to calculate the whole weeks easily (without iterating over all of the dates). All we need to do then is to add the working days that fall before the start and end of this core range.

public static int CalculateWorkingDays(
    DateTime startDate, 
    DateTime endDate, 
    IList<DateTime> holidays, 
    DayOfWeek firstDayOfWeek,
    DayOfWeek lastDayOfWeek)
{
    // Make sure the defined working days run contiguously
    if (lastDayOfWeek < firstDayOfWeek)
    {
        throw new Exception("Last day of week cannot fall before first day of week!");
    }

    // Create a list of the days of the week that make-up the weekend by working back
    // from the firstDayOfWeek and forward from lastDayOfWeek to get the start and end
    // the weekend
    var weekendStart = lastDayOfWeek == DayOfWeek.Saturday ? DayOfWeek.Sunday : lastDayOfWeek + 1;
    var weekendEnd = firstDayOfWeek == DayOfWeek.Sunday ? DayOfWeek.Saturday : firstDayOfWeek - 1;
    var weekendDays = new List<DayOfWeek>();

    var w = weekendStart;
    do {
        weekendDays.Add(w);
        if (w == weekendEnd) break;
        w = (w == DayOfWeek.Saturday) ? DayOfWeek.Sunday : w + 1;
    } while (true);


    // Force simple dates - no time
    startDate = startDate.Date;
    endDate = endDate.Date;

    // Ensure a progessive date range
    if (endDate < startDate)
    {
        var t = startDate;
        startDate = endDate;
        endDate = t;
    }

    // setup some working variables and constants
    const int daysInWeek = 7;           // yeah - really!
    var actualStartDate = startDate;    // this will end up on startOfWeek boundary
    var actualEndDate = endDate;        // this will end up on weekendEnd boundary
    int workingDaysInWeek = daysInWeek - weekendDays.Count;

    int workingDays = 0;        // the result we are trying to find
    int leadingDays = 0;        // the number of working days leading up to the firstDayOfWeek boundary
    int trailingDays = 0;       // the number of working days counting back to the weekendEnd boundary

    // Calculate leading working days
    // if we aren't on the firstDayOfWeek we need to step forward to the nearest
    if (startDate.DayOfWeek != firstDayOfWeek)
    {
        var d = startDate;
        do {
            if (d.DayOfWeek == firstDayOfWeek || d >= endDate)
            {
                actualStartDate = d;
                break;  
            }
            if (!weekendDays.Contains(d.DayOfWeek))
            {
                leadingDays++;
            }
            d = d.AddDays(1);
        } while(true);
    }

    // Calculate trailing working days
    // if we aren't on the weekendEnd we step back to the nearest
    if (endDate >= actualStartDate && endDate.DayOfWeek != weekendEnd)
    {
        var d = endDate;
        do {
            if (d.DayOfWeek == weekendEnd || d < actualStartDate)
            {
                actualEndDate = d;
                break;  
            }
            if (!weekendDays.Contains(d.DayOfWeek))
            {
                trailingDays++;
            }
            d = d.AddDays(-1);
        } while(true);
    }

    // Calculate the inclusive number of days between the actualStartDate and the actualEndDate
    var coreDays = (actualEndDate - actualStartDate).Days + 1;
    var noWeeks =  coreDays / daysInWeek;

    // add together leading, core and trailing days
    workingDays +=  noWeeks * workingDaysInWeek;
    workingDays += leadingDays;
    workingDays += trailingDays;

    // Finally remove any holidays that fall within the range.
    if (holidays != null)
    {
        workingDays -= holidays.Count(h => h >= startDate && (h <= endDate));
    }

    return workingDays;
}

Answer 5

You just have to iterate through each day in the time range and subtract a day from the counter if its a Saturday or a Sunday.

    private float SubtractWeekend(DateTime start, DateTime end) {
        float totaldays = (end.Date - start.Date).Days;
        var iterationVal = totalDays;
        for (int i = 0; i <= iterationVal; i++) {
            int dayVal = (int)start.Date.AddDays(i).DayOfWeek;
            if(dayVal == 6 || dayVal == 0) {
                // saturday or sunday
                totalDays--;
            }
        }
        return totalDays;
    }

Answer 6

Here's a quick sample code. It's a class method, so will only work inside of your class. If you want it to be static, change the signature to private static (or public static).

    private IEnumerable<DateTime> GetWorkingDays(DateTime sd, DateTime ed)
    {
        for (var d = sd; d <= ed; d = d.AddDays(1))
            if (d.DayOfWeek != DayOfWeek.Saturday && d.DayOfWeek != DayOfWeek.Sunday)
                yield return d;
    }

This method creates a loop variable d, initializes it to the start day, sd, then increments by one day each iteration (d = d.AddDays(1)).

It returns the desired values using yield, which creates an iterator. The cool thing about iterators is that they don't hold all of the values of the IEnumerable in memory, only calling each one sequentially. This means that you can call this method from the dawn of time to now without having to worry about running out of memory.