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

Yet another approach for calculating business days, not considering holidays, but taking into account the time of day returning a fractional amount of days:

public static double GetBusinessDays(DateTime startD, DateTime endD)
{
    while (IsWeekend(startD))
        startD = startD.Date.AddDays(1);

    while (IsWeekend(endD))
        endD = endD.Date.AddDays(-1);

    var bussDays = (endD - startD).TotalDays -
        (2 * ((int)(endD - startD).TotalDays / 7)) -
        (startD.DayOfWeek > endD.DayOfWeek ? 2 : 0);

    return bussDays;
}

public static bool IsWeekend(DateTime d)
{
    return d.DayOfWeek == DayOfWeek.Saturday || d.DayOfWeek == DayOfWeek.Sunday;
}

You can fiddle with it here: https://rextester.com/ASHRS53997

Answer 2

This is a generic solution.

startdayvalue is day number of start date.

weekendday_1 is day numner of week end.

day number - MON - 1, TUE - 2, ... SAT - 6, SUN -7.

difference is difference between two dates..

Example : Start Date : 4 April, 2013, End Date : 14 April, 2013

Difference : 10, startdayvalue : 4, weekendday_1 : 7 (if SUNDAY is a weekend for you.)

This will give you number of holidays.

No of business day = (Difference + 1) - holiday1

    if (startdayvalue > weekendday_1)
    {

        if (difference > ((7 - startdayvalue) + weekendday_1))
        {
            holiday1 = (difference - ((7 - startdayvalue) + weekendday_1)) / 7;
            holiday1 = holiday1 + 1;
        }
        else
        {
            holiday1 = 0;
        }
    }
    else if (startdayvalue < weekendday_1)
    {

        if (difference > (weekendday_1 - startdayvalue))
        {
            holiday1 = (difference - (weekendday_1 - startdayvalue)) / 7;
            holiday1 = holiday1 + 1;
        }
        else if (difference == (weekendday_1 - startdayvalue))
        {
            holiday1 = 1;
        }
        else
        {
            holiday1 = 0;
        }
    }
    else
    {
        holiday1 = difference / 7;
        holiday1 = holiday1 + 1;
    }

Answer 3

Based on the comment marked as answer and patch recommended , as well as -> This version wants to convert the Days to Business-Hours ... Considers Same day hours as well.

 /// <summary>
    /// Calculates number of business days, taking into account:
    ///  - weekends (Saturdays and Sundays)
    ///  - bank holidays in the middle of the week
    /// </summary>
    /// <param name="firstDay">First day in the time interval</param>
    /// <param name="lastDay">Last day in the time interval</param>
    /// <param name="bankHolidays">List of bank holidays excluding weekends</param>
    /// <returns>Number of business hours during the 'span'</returns>
    public static int BusinessHoursUntil(DateTime firstDay, DateTime lastDay, params DateTime[] bankHolidays)
    {
        var original_firstDay = firstDay;
        var original_lastDay = lastDay;
        firstDay = firstDay.Date;
        lastDay = lastDay.Date;
        if (firstDay > lastDay)
            return -1; //// throw new ArgumentException("Incorrect last day " + lastDay);

        TimeSpan span = lastDay - firstDay;
        int businessDays = span.Days + 1;
        int fullWeekCount = businessDays / 7;
        // find out if there are weekends during the time exceedng the full weeks
        if (businessDays > fullWeekCount * 7)
        {
            // we are here to find out if there is a 1-day or 2-days weekend
            // in the time interval remaining after subtracting the complete weeks
            int firstDayOfWeek = firstDay.DayOfWeek == DayOfWeek.Sunday ? 7 : (int)firstDay.DayOfWeek;
            int lastDayOfWeek = lastDay.DayOfWeek == DayOfWeek.Sunday ? 7 : (int)lastDay.DayOfWeek;

            if (lastDayOfWeek < firstDayOfWeek)
                lastDayOfWeek += 7;
            if (firstDayOfWeek <= 6)
            {
                if (lastDayOfWeek >= 7)// Both Saturday and Sunday are in the remaining time interval
                    businessDays -= 2;
                else if (lastDayOfWeek >= 6)// Only Saturday is in the remaining time interval
                    businessDays -= 1;
            }
            else if (firstDayOfWeek <= 7 && lastDayOfWeek >= 7)// Only Sunday is in the remaining time interval
                businessDays -= 1;
        }

        // subtract the weekends during the full weeks in the interval
        businessDays -= fullWeekCount + fullWeekCount;

        if (bankHolidays != null && bankHolidays.Any())
        {
            // subtract the number of bank holidays during the time interval
            foreach (DateTime bankHoliday in bankHolidays)
            {
                DateTime bh = bankHoliday.Date;
                if (firstDay <= bh && bh <= lastDay)
                    --businessDays;
            }
        }

        int total_business_hours = 0;
        if (firstDay.Date == lastDay.Date)
        {//If on the same day, go granular with Hours from the Orginial_*Day values
            total_business_hours = (int)(original_lastDay - original_firstDay).TotalHours;
        }
        else
        {//Convert Business-Days to TotalHours
            total_business_hours = (int)(firstDay.AddDays(businessDays).AddHours(firstDay.Hour) - firstDay).TotalHours;
        }
        return total_business_hours;
    }

Answer 4

Define an Extension Method on DateTime like so:

public static class DateTimeExtensions
{
    public static bool IsWorkingDay(this DateTime date)
    {
        return date.DayOfWeek != DayOfWeek.Saturday
            && date.DayOfWeek != DayOfWeek.Sunday;
    }
}

Then, use is within a Where clause to filter a broader list of dates:

var allDates = GetDates(); // method which returns a list of dates

// filter dates by working day's  
var countOfWorkDays = allDates
     .Where(day => day.IsWorkingDay())
     .Count() ;

Answer 5

Ok. I think it's time to post the right answer:

public static double GetBusinessDays(DateTime startD, DateTime endD)
{
    double calcBusinessDays =
        1 + ((endD - startD).TotalDays * 5 -
        (startD.DayOfWeek - endD.DayOfWeek) * 2) / 7;

    if (endD.DayOfWeek == DayOfWeek.Saturday) calcBusinessDays--;
    if (startD.DayOfWeek == DayOfWeek.Sunday) calcBusinessDays--;

    return calcBusinessDays;
}

Original Source:

http://alecpojidaev.wordpress.com/2009/10/29/work-days-calculation-with-c/

P.S. Solutions posted above making me sic for some reason.

Answer 6

I came up with the following solution

var dateStart = new DateTime(2019,01,10);
var dateEnd = new DateTime(2019,01,31);

var timeBetween = (dateEnd - dateStart).TotalDays + 1;
int numberOf7DayWeeks = (int)(timeBetween / 7);
int numberOfWeekendDays = numberOf7DayWeeks * 2;
int workingDays =(int)( timeBetween - numberOfWeekendDays);

if(dateStart.DayOfWeek == DayOfWeek.Saturday || dateEnd.DayOfWeek == DayOfWeek.Sunday){
    workingDays -=2;
}       
if(dateStart.DayOfWeek == DayOfWeek.Sunday || dateEnd.DayOfWeek == DayOfWeek.Saturday){
    workingDays -=1;
}