Find the last thursday of a month between two dates C#

Question

User457850011 posted

<div id="threadActionMenu" class="menu thread"> <div value="unsubscribe"> I am trying to display the start and end date for  the last Thursday of every month between two days. I am able to get the last Thursday for each month successfully but not able to display the start and the end date. Below is my code.</div> </div> <div class="messageContent"> <div class="container"> <div class="body">

Any help will be appreciated.

public class BusinessWeekDays
{
public DateTime StartDateMonth;
public DateTime EndMonth;
} 

static void Main(string[] args)
{
var StartDate = DateTime.Parse("04/25/2019");
var SeriesEndDate = DateTime.Parse("09/30/2019");

var months = new List<businessweekdays>();
var Monthly = 1;
for (var i = StartDate; i < SeriesEndDate; i = i.AddMonths(Monthly))
{
const int thursday = 4;
const int dayDiff = 7 - thursday;

var Day = DateTime.DaysInMonth(i.Year, i.Month);
var DayOfWeek = (int)new DateTime(i.Year, i.Month, Day).DayOfWeek;

var _dtNew = new DateTime(i.Year, i.Month, Day).AddDays(-(DayOfWeek < thursday ? DayOfWeek + dayDiff : DayOfWeek - thursday));
var e = _dtNew.AddMonths(+1).AddDays(-2);----> This line is incorrect and I need help here.
months.Add(new BusinessWeekDays{ StartDateMonth = _dtNew, EndMonth = e});
Console.WriteLine(months);
}
}
}

The purpose of these two line:

var e = _dtNew.AddMonths(+1).AddDays(-2);
months.Add(new BusinessWeekDays{ StartDateMonth = _dtNew, EndMonth = e});

are just to display the start and the end date for each month and that is where I am having an issue. So for example I know the start date is 04/25/2019

the following month Last Thursday is 5/30/2019

the next month last Thursday is 6/27/2019

I just want to display

StartDate EnDate

4/25/2019 5/30/2019

startdate 6/27/2019

 

Answer 1

User303363814 posted

I have run your code and it shows six lists of pairs of dates.  Can you explain what is wrong with the result that your code generates?

5List<BusinessWeekDays> (1 item)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM

5List<BusinessWeekDays> (2 items)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM

5List<BusinessWeekDays> (3 items)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM

5List<BusinessWeekDays> (4 items)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM
25/07/2019 12:00:00 AM	23/08/2019 12:00:00 AM

5List<BusinessWeekDays> (5 items)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM
25/07/2019 12:00:00 AM	23/08/2019 12:00:00 AM
29/08/2019 12:00:00 AM	27/09/2019 12:00:00 AM

5List<BusinessWeekDays> (6 items)44
StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM
25/07/2019 12:00:00 AM	23/08/2019 12:00:00 AM
29/08/2019 12:00:00 AM	27/09/2019 12:00:00 AM
26/09/2019 12:00:00 AM	24/10/2019 12:00:00 AM

Answer 2

User457850011 posted

Hi

Thanks for your response. The idea is I am supposed to get the last Thursday of every month from Start Date to End Date from  04/25/2019 all the way to 9/30/2019

This line of my code var e = _dtNew.AddMonths(+1).AddDays(-2); is incorrect because it is failing when there is  31 days in month while it works for the moths where we have 30 days.As in case of 30 days it will add 27 days ( 4 weeks) while in case of 31 days it will add 29 days (4 weeks + 1)

StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM --Incorrect is not the last Thursday. The last Thursday of May is 30/05/2019
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM---Incorrect because last Thursday of June is 27/06/2019
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM--correct
25/07/2019 12:00:00 AM	23/08/2019 12:00:00 AM----Incorrect because the last Thursday of August is 29/08/2019
29/08/2019 12:00:00 AM	27/09/2019 12:00:00 AM-----Incorrect because the last Thursday of September is  26/09/2019
26/09/2019 12:00:00 AM	24/10/2019 12:00:00 AM-----Incorrect because the last Thursday of October is 31/10/2019

Answer 3

User36583972 posted

Hi

Thanks for your response. The idea is I am supposed to get the last Thursday of every month from Start Date to End Date from  04/25/2019 all the way to 9/30/2019

This line of my code var e = _dtNew.AddMonths(+1).AddDays(-2); is incorrect because it is failing when there is  31 days in month while it works for the moths where we have 30 days.As in case of 30 days it will add 27 days ( 4 weeks) while in case of 31 days it will add 29 days (4 weeks + 1)

StartDateMonth	EndMonth
25/04/2019 12:00:00 AM	23/05/2019 12:00:00 AM --Incorrect is not the last Thursday. The last Thursday of May is 30/05/2019
30/05/2019 12:00:00 AM	28/06/2019 12:00:00 AM---Incorrect because last Thursday of June is 27/06/2019
27/06/2019 12:00:00 AM	25/07/2019 12:00:00 AM--correct
25/07/2019 12:00:00 AM	23/08/2019 12:00:00 AM----Incorrect because the last Thursday of August is 29/08/2019
29/08/2019 12:00:00 AM	27/09/2019 12:00:00 AM-----Incorrect because the last Thursday of September is  26/09/2019
26/09/2019 12:00:00 AM	24/10/2019 12:00:00 AM-----Incorrect because the last Thursday of October is 31/10/2019

Hi denkyira,

You can refer the following sample:

     static void Main(string[] args)
        {
            var StartDate = DateTime.Parse("04/25/2019");
            var SeriesEndDate = DateTime.Parse("09/30/2019");

            var months = new List<BusinessWeekDays>();
            var Monthly = 1;
            for (var i = StartDate; i < SeriesEndDate; i = i.AddMonths(Monthly))
            {
                const int thursday = 4;
                const int dayDiff = 7 - thursday;

                var Day = DateTime.DaysInMonth(i.Year, i.Month);
                var DayOfWeek = (int)new DateTime(i.Year, i.Month, Day).DayOfWeek;

                var _dtNew = new DateTime(i.Year, i.Month, Day).AddDays(-(DayOfWeek < thursday ? DayOfWeek + dayDiff : DayOfWeek - thursday));
                //var e = _dtNew.AddMonths(+1).AddDays(-2);
                var e = returnEndMonth(_dtNew);
                months.Add(new BusinessWeekDays { StartDateMonth = _dtNew, EndMonth = e });

            }

            foreach (var item in months)
            {
                Console.WriteLine("StartDateMonth:" + item.StartDateMonth + "; EndMonth:" + item.EndMonth);
            }


            Console.ReadLine();
        }

        public static DateTime returnEndMonth(DateTime sdt)
        {
            int alldays = DateTime.DaysInMonth(sdt.Year, sdt.AddMonths(1).Month);
            DateTime endtime = new DateTime(sdt.Year, sdt.AddMonths(1).Month, alldays);
            for(int i=0 ; i<= alldays; i++ )
            {
                if(endtime.AddDays(-i).DayOfWeek.ToString()== "Thursday")
                {
                    endtime = endtime.AddDays(-i);
                    break;
                }
            }          
            return endtime;
        }

Best Regards

Yong Lu

Answer 4

User457850011 posted

Hi Lu

Thanks a millions times. Your code works perfectly correct.