tommy.blog

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: C#.

# posted @ 12:46

Comments:

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.

# posted by

Martin Plante : 17 February, 2006 13:43

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.

# posted by

Tommy Carlier : 17 February, 2006 14:02

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.

# posted by

Anonymous : 04 May, 2006 05:49

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);

# posted by

Tommy Carlier : 04 May, 2006 08:31