It seems that the DateTimeSpan solution pleases a lot of people. I don't know. Let's consider the:
BeginDate = 1972/2/29 EndDate = 1972/4/28.
The DateTimeSpan based answer is:
1 year(s), 2 month(s) and 0 day(s)
I implemented a method and based on that the answer is:
1 year(s), 1 month(s) and 28 day(s)
Clearly there are not 2 full months there. I would say that because we are at the end of the month of the begin date what's left is actually the full month of March plus the number of days passed in the month of the end date (April), so 1 month and 28 days.
If you read so far and you are intrigued I posted the method below. I am explaining in the comments the assumptions I make because how many months, the concept of months is such a moving target. Test it many times and see if the answers make sense. I usually choose test dates in adjacent years and once I verify an answer I move a day or two back and forth. So far it looks good, I'm sure you'll find some bugs :D. The code might look a bit rough but I hope it is clear enough:
static void Main(string[] args) { DateTime EndDate = new DateTime(1973, 4, 28); DateTime BeginDate = new DateTime(1972, 2, 29); int years, months, days; GetYearsMonthsDays(EndDate, BeginDate, out years, out months, out days); Console.WriteLine($"{years} year(s), {months} month(s) and {days} day(s)"); } /// <summary> /// Calculates how many years, months and days are between two dates. /// </summary> /// <remarks> /// The fundamental idea here is that most of the time all of us agree /// that a month has passed today since the same day of the previous month. /// A particular case is when both days are the last days of their respective months /// when again we can say one month has passed. /// In the following cases the idea of a month is a moving target. /// - When only the beginning date is the last day of the month then we're left just with /// a number of days from the next month equal to the day of the month that end date represent /// - When only the end date is the last day of its respective month we clearly have a /// whole month plus a few days after the the day of the beginning date until the end of its /// respective months /// In all the other cases we'll check /// - beginingDay > endDay -> less then a month just daysToEndofBeginingMonth + dayofTheEndMonth /// - beginingDay < endDay -> full month + (endDay - beginingDay) /// - beginingDay == endDay -> one full month 0 days /// /// </remarks> /// private static void GetYearsMonthsDays(DateTime EndDate, DateTime BeginDate, out int years, out int months, out int days ) { var beginMonthDays = DateTime.DaysInMonth(BeginDate.Year, BeginDate.Month); var endMonthDays = DateTime.DaysInMonth(EndDate.Year, EndDate.Month); // get the full years years = EndDate.Year - BeginDate.Year - 1; // how many full months in the first year var firstYearMonths = 12 - BeginDate.Month; // how many full months in the last year var endYearMonths = EndDate.Month - 1; // full months months = firstYearMonths + endYearMonths; days = 0; // Particular end of month cases if(beginMonthDays == BeginDate.Day && endMonthDays == EndDate.Day) { months++; } else if(beginMonthDays == BeginDate.Day) { days += EndDate.Day; } else if(endMonthDays == EndDate.Day) { days += beginMonthDays - BeginDate.Day; } // For all the other cases else if(EndDate.Day > BeginDate.Day) { months++; days += EndDate.Day - BeginDate.Day; } else if(EndDate.Day < BeginDate.Day) { days += beginMonthDays - BeginDate.Day; days += EndDate.Day; } else { months++; } if(months >= 12) { years++; months = months - 12; } }