Date Difference

Question

I have two dates and want difference result in months

currently i m using :

dtResult = dtExp.Subtract(dtReg);

intDays = dtResult.Days;
months = intDays / 30;

but it is giving wrong ans when there is one month difference....
can anyone help me

thx in advance

Vulpes · Answer

Here's a technique I've used for many years to get the difference in months between two dates. It works by assuming that there are 31 days in each month and therefore 372 days in a whole year: using System; class Test { static void Main() { DateTime dt1 = new DateTime(2011 2 28); DateTime dt2 = new DateTime(2011 3 28); int months = DateDiffInMonths(dt1 dt2); Console.WriteLine(months); // 1 Console.ReadKey(); } static int DateDiffInMonths(DateTime dt1 DateTime dt2) { int date1 = dt1.Year * 372 + dt1.Month * 31 + dt1.Day; int date2 = dt2.Year * 372 + dt2.Month * 31 + dt2.Day; return (date2 - date1)/31; } } If you would like to assume that 28 February 2011 to 27 March 2011 should be regarded as a whole month (which it is in some applications) then simply add 1 to date2. Notice that the routine automatically compensates for leap years.

Suthish Nair · Answer

Ok Another way.. Note: This work as same as SQL Server DateDiff method. System.Data.Linq.SqlClient.SqlMethods.DateDiffMonth(DateTime.Parse( 01-Feb-2011) DateTime.Parse( 02-Apr-2011)) ==> 2 System.Data.Linq.SqlClient.SqlMethods.DateDiffMonth(DateTime.Parse( 01-Feb-2011) DateTime.Parse( 30-Mar-2011)) ==> 1 System.Data.Linq.SqlClient.SqlMethods.DateDiffMonth(DateTime.Parse( 01-Feb-2011) DateTime.Parse( 27-Feb-2011)) ==> 0 System.Data.Linq.SqlClient.SqlMethods.DateDiffMonth(DateTime.Parse( 01-Feb-2011) DateTime.Parse( 28-Feb-2011)) ==> 0 System.Data.Linq.SqlClient.SqlMethods.DateDiffMonth(DateTime.Parse( 01-Feb-2011) DateTime.Parse( 01-Mar-2011)) ==> 1

Amruta Kirdat · Answer

thx 4 reply... yes i can chk leap yr n use if else.... but my basic question is dont we have any inbuilt functions to chk difference in month afterall m working on .net not vb....

Mamta M · Answer

Then all you need to do is a write an if-else logic before the division takes place: eg: if (dtExp.Month == 2) { months = intDays / 28; } else { months = intDays / 30; } But this is not complete yet because you further need to check if it is a leap year in which case you will divide by 29. I guess you got the basic logic now u can write the remaining code for leap year check by yourself.

Amruta Kirdat · Answer

hii sry 4 late reply due to some net prob was unable to reply.....but m back... thx mamtasuthisvulpes for your replies... vulpes got exactly want i wann to say.... if there are 28 days and m dividing by 30 den it is giving 0 months which is wrong ans....

Mamta M · Answer

Vulpes: you are right there. Suthish: I understood your point too. That's good too. Let's wait and see her reply.

Vulpes · Answer

I wondered whether she meant that dividing the days by 30 doesn't always give the correct 'intuitive' answer. For example if you go from 28 February to 28 March then most people would say that's a one month interval. However the difference in days is only 28 (using TimeSpan) and so her calculation would give 0 rather than 1 month.

Suthish Nair · Answer

The error might she might getting because of the negative values (days). She needs to check or define logic for on which dates she needs to find the difference. Thats why i given the sample in DateTime.Today date. And also second line of code helps to find out the number of days in a month (30 31 28 etc..). hope you understood what i was trying to say. I want her to work on the code so she can learn by herself.

Mamta M · Answer

Suthish How is your answer helpful to her? She has already used Days and already divided the days by 30 to get the month. So she is aware of the logic but it is not working according to her for some particular values. So instead of giving her a vague reply about the functions to use we can instead find out which values she is testing with. I tried the code which is similar to her code and it is working successfully so all we need to do now is find out what was the value which gave her incorrect output.

Suthish Nair · Answer

int i = DateTime.Today.Subtract(DateTime.Parse(01-Mar-2011)).Days will give difference days. System.DateTime.DaysInMonth(DateTime.Now.Year DateTime.Now.Month) will give total number of days in a month. Now build your logic.

Mamta M · Answer

Hi I tried your code as follows (adding my own data types) and it worked successfully for all values: DateTime dtExp dtReg; TimeSpan dtResult; Console.WriteLine(Enter date ); dtExp = Convert.ToDateTime(Console.ReadLine()); Console.WriteLine(Enter date ); dtReg = Convert.ToDateTime(Console.ReadLine()); dtResult = dtExp.Subtract(dtReg); int intDays = dtResult.Days; float months = intDays / 30; Console.WriteLine(months); So with what values are you getting wrong answer? Can you let me know?