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hi.
i have year,month and week number of month and week day.
for example:
1994,jun,week number in month:4, monday.
how can i get date?
Posted

The solution is country dependent !
In Europe week start on Monday, in USA week start on Sunday.

This is not a programming problem, it is a mathematical problem.

You have to find the algorithm for your country because the week don't start the same day in every country. I suggest to use Wikipedia.
https://en.wikipedia.org/wiki/ISO_week_date[^]
https://en.wikipedia.org/wiki/Week[^]

Conventions in your date data may also play in the solution:
- how are you numbering the first week of a month when it is only 1 or 2 days ?
   
v3
Comments
PIEBALDconsult 29-Aug-15 18:58pm
   
"in USA week start on Sunday"

No. There are International Standards that specify Monday. These apply to the U.S.
Patrice T 29-Aug-15 19:19pm
   
Wikipedia disagree with you :)
https://en.wikipedia.org/wiki/Week
It is mostly maths, try this example to find the date for the Wednesday on 4th week of February 2016. Test it with other dates and parameter, say 5th week, it will cross over to March.
using System;

public class Program
{
	public static void Main()
	{
		DateTime dt = new DateTime(2016, 2, 1); // create the start date of the month and year
		DayOfWeek firstDayOfWeekofMonth = dt.DayOfWeek; // Find out the day of week for that date
		int myWeekNumInMonth = 4; // You want the 4th week, this may cross over to the following month!
		string myDayOfWeek = "Wednesday";  // You want Wednesday
		int myDayOfWeekInt = day2Int(myDayOfWeek);
		int diff = myDayOfWeekInt - (int)firstDayOfWeekofMonth;
		Console.WriteLine("The answer is {0:d}.", dt.AddDays(7 * (myWeekNumInMonth - 1) + diff));
	}

	public static int day2Int(string dayOfWeek)
	{
		switch (dayOfWeek)
		{
			case "Sunday":
				return 0;
			case "Monday":
				return 1;
			case "Tuesday":
				return 2;
			case "Wednesday":
				return 3;
			// Finish the rest yourself
			default:
				return -1; // Do error checking
		}
	}
}

Find out more:
1. DayOfWeek Enumeration[^]
2. DateTime.AddDays Method[^]
   
v2
Comments
rahman_jalayer 30-Aug-15 10:52am
   
thanks a lot mr. Peter Leow.
it works great.
thank you.
Peter Leow 31-Aug-15 5:23am
   
You are welcome.

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