How to display difference between two dates as 00Y 00M

Question

Given two DateTimes in C#, how can I display the difference in years and months?

I can do basic arithmatic on the timespan that comes from a simple subtraction but this won't take into account the differing lengths of months, leap years etc.

Thanks for any help.

Answer 1

You could try this:

DateTime date1 = new DateTime(1954, 7, 30);
DateTime today = DateTime.Now;

TimeSpan span = today - date1;
DateTime age = DateTime.MinValue + span;

int years = age.Year - 1;
int months = age.Month - 1;
int days = age.Day - 1;

Console.WriteLine("years: {0}, months: {1}, days: {2}", years, months, days);

Answer 2

Because the underlying representation is measured in 100-nanosecond ticks since 12:00 midnight, January 1, 1 A.D., a subtraction will handle leap years etc. quite correctly:

DateTime date1 = ...
DateTime date2 = ...

// date2 must be after date1

TimeSpan difference = date2.Subtract(date1);
DateTime age=new DateTime(tsAge.Ticks); 

int years = age.Years - 1;
int months = age.Month - 1;

Console.WriteLine("{0}Y, {1}M", years, months);

Answer 3

Different length of month? Which month should it take? the time span is not bound to a certain year or month in the year. You can only count the days between two dates:

Timspan span = date2 - date1;

Console.Writeline("Days between date1 and date2: {0}", span.Days);

Counting from DateTime.MinValue just take the year 0001 as start and counts the months from January. I don't think that this is of practical use.

EDIT:

Had another idea. You can count the month since date1:

// primitive, inelegant, but should work if date1 < date2
int years = date2.Year - date1.Year;
int month = date2.Month - date1.Month;
if (month < 0) 
{
  years -= 1;
  month += 12;
}
Console.Writeline("{0}Y {1}M", years, month);

The problem here is that you just ignore the days. After all it's not a good solution.

Answer 4

FWIW here's what i've ended up with

        DateTime servicelength = new DateTime(DateTime.Now.Subtract(employee.StartDate).Ticks);
        LengthOfService.Text = String.Format("{0}Y {1}M", servicelength.Year - 1, servicelength.Month - 1);