Calculate How Many Mondays in a Particular Month

Abhishek Sur

Do like this :

int year = 2009;
int month = 2;
int nos = 0;
DateTime startDate = new DateTime(year, month, 1);
DateTime endDate = startDate.AddMonths(1);
while (startDate.DayOfWeek != DayOfWeek.Monday)
startDate = startDate.AddDays(1);
for (DateTime result = startDate; result < endDate; result = result.AddDays(7))
nos+=1;

//Print nos.

Hope this help. Cheers.

Abhishek Sur **Don't forget to click "Good Answer" if you like this Solution.

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musefan

Here's a method you could use...

int CountDaysInMonth(int month, int year, DayOfWeek dayToCount)
{
DateTime dt = new DateTime(year, month, 1);
int result = 0;
for(int i = 0; i < DateTime.DaysInMonth(year, month); i++)
{
if(dt.DayOfWeek == dayToCount)
result++;
dt.AddDays(1);
}
return result;
}

Life goes very fast. Tomorrow, today is already yesterday.

musefan

Improved...

int CountDaysInMonth(int month, int year, DayOfWeek dayToCount)
{
DateTime dt = new DateTime(year, month, 1);
int firstInstance = 1;
if((int)dt.DayOfWeek > (int)dayToCount)
firstInstance += (7 - (int)dt.DayOfWeek) + (int)dayToCount;
else if((int)dt.DayOfWeek < (int)dayToCount)
firstInstance += (int)dayToCount - (int)dt.DayOfWeek;
return firstInstance <= (DateTime.DaysInMonth(month, year) - 28) ? 5 : 4;
}

...I think the logic is right. [EDIT] That was way off, I fixed now... I think!

Life goes very fast. Tomorrow, today is already yesterday.

Lost User

I'm not too sure about the various constants, but it looks like The Right Way to do it

PIEBALDconsult

Not everyone picks up on these things.

musefan

On second thoughts, it does not look much improved :laugh: The constants are OK, they will never need to change

Life goes very fast. Tomorrow, today is already yesterday.

musefan

What??? It does not work? What's with the 'Bad Answer' again?

Life goes very fast. Tomorrow, today is already yesterday.

Luc Pattyn

Obviously you do not need any loop or conditional for this. Have a look at:

int mondays=(DateTime.DaysInMonth(year, month) + (int)new DateTime(year, month, 6).DayOfWeek) / 7;

What remains of this homework is for you to figure out why the expression is what it is! :)

Luc Pattyn [Forum Guidelines] [My Articles]

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

Luc Pattyn

harold aptroot wrote:

it looks like The Right Way to do it

really? :)

Luc Pattyn [Forum Guidelines] [My Articles]

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

Lost User

*reconsiders* Yes? No seriously, no matter how wrong it was, not having a loop made it much closer than all those other entries..

PIEBALDconsult

No, it's obvious that no loop is required, but I still have two conditionals in mine. I, like some of the others, am not content to hard code Monday, but would prefer to take the day of the week as a parameter. I haven't tried yours yet, but I don't see how it can be a general solution for any specified day of the week. On the whole, I expect the OP's teacher only wants to prove that he's smarter than his students.

Luc Pattyn

IMO it works for all years and months, I checked for this year only. With a day-of-week parameter it becomes:

int Xdays=(DateTime.DaysInMonth(year, month) + (int)new DateTime(year, month, 7-dayOfWeek).DayOfWeek) / 7;

where dayOfWeek is 0=SU, 1=MO, ... 6=SA [ADDED] so you can also use (int)DayOfWeek [/ADDED] :)

Luc Pattyn [Forum Guidelines] [My Articles]

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

modified on Wednesday, November 18, 2009 3:36 PM

Luc Pattyn

PIEBALDconsult wrote:

I expect the OP's teacher only wants to prove that he's smarter than his students

The teacher may be shaded then by a cheating student. :laugh:

Luc Pattyn [Forum Guidelines] [My Articles]

I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages

PIEBALDconsult

What I came up with is similar to that:

public static int
F
(
int Year
,
int Month
,
System.DayOfWeek DayOfWeek
)
{
int d = (int) DayOfWeek - (int) (new System.DateTime ( Year , Month , 1 )).DayOfWeek ;

if ( d < 0 )
{
    d += 7 ;
}

int n = System.DateTime.DaysInMonth ( Year , Month ) - 28 ;

return ( d < n ? 5 : 4 ) ;

}

cdpace

Lol guys Thank you very much for the help ;) but actually this ain't for homework hehe, this is part of a payroll system that I am developing at work and with the deadline stress and from being tired because been programming 8 hours strait i couldn't find a solution for this so i turned to some help ;) hehe thank you again guys.