2006-02-17

Years, months and days between 2 dates

Here you can find a method that can calculate the years, months and days between 2 dates. 
/// <summary>Calculates the difference between 2 dates in years, months and days.</summary>
/// <param name="startDate">The start date.</param>
/// <param name="endDate">The end date.</param>
/// <param name="years">The variable that will contain the years.</param>
/// <param name="months">The variable that will contain the months.</param>
/// <param name="days">The variable that will contain the days.</param>

public static void DateDifference(DateTime startDate, DateTime endDate, out int years, out int months, out int days)
{
    years = endDate.Year - startDate.Year;
    months = endDate.Month - startDate.Month;
    days = endDate.Day - startDate.Day;

    if (days < 0) months -= 1;
    while (months < 0) { months += 12; years -= 1; }

    TimeSpan timeSpan = endDate - startDate.AddYears(years).AddMonths(months);
    days = (int)Math.Round(timeSpan.TotalDays);
}
And here is a method that uses the previous method and returns a string representation of the difference: 
/// <summary>Calculates the difference between 2 dates, and returns it as a formatted string.</summary>
/// <param name="startDate">The start date.</param>
/// <param name="endDate">The end date.</param>
/// <returns>The formatted string that represents the calculated difference.</returns>

public static string DateDifference(DateTime startDate, DateTime endDate)
{
    int years, months, days;
    DateDifference(startDate, endDate, out years, out months, out days);
    return 
        ((years != 0 ? years.ToString() + "y " : "") +
        (months != 0 ? months.ToString() + "m " : "") +
        (days != 0 ? days.ToString() + "d" : "")).TrimEnd();
}
Tags: .
Posted by Tommy Carlier at 12:46

4 comments:

Martin Plante said...

Watch out! If startDate and endDate are not in UTC, this can return invalid results. For example, one date may be in daylight saving, while the other isn't. Their difference will miss or have one extra hour.

17 February, 2006 13:43
Tommy Carlier said...

Good point. I hadn't thought about that situation, because I thought it was logical that if you compare DateTimes, they should both use the same timezone, or be UTC.

17 February, 2006 14:02
Anonymous said...

One of us must be smoking..something that I don't know what it is. Try your code with Ending Date 3/1/2006 and 7/31/2002 as starting date.

04 May, 2006 05:49
Tommy Carlier said...

Anonymous, I just tried your example and I see nothing wrong.
I get 3 years, 7 months and 1 day.
If I call startDate.AddYears(3).AddMonths(7).AddDays(1), I get the right end date (March 1st 2006).
I used this code snippet:
DateTime start = new DateTime(2002, 7, 31);
DateTime end = new DateTime(2006, 3, 1);
int years, months, days;
DateDifference(start, end, out years, out months, out days);
Console.WriteLine("{0}y {1}m {2}d", years, months, days);
DateTime newEnd = start.AddYears(years).AddMonths(months).AddDays(days);
Console.WriteLine(newEnd);

04 May, 2006 08:31

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