DateDiff() function in C#

By Fons Sonnemans, 11-feb-2004

I have written the following DateDiff() function in C#. VB.NET users already had it using the Micrsoft.VisualBasic.dll assembly. Now you can use it without referencing this 'ugly' extra assembly.

using System;

namespace ReflectionIT.System {

    public enum DateInterval {

    public class DateTimeUtil {

        public static long DateDiff(DateInterval interval, DateTime date1, DateTime date2) {

            TimeSpan ts = date2 - date1;

            switch (interval) {
                case DateInterval.Year:
                    return date2.Year - date1.Year;
                case DateInterval.Month:
                    return (date2.Month - date1.Month) + (12 * (date2.Year - date1.Year));
                case DateInterval.Weekday:
                    return Fix(ts.TotalDays) / 7;
                case DateInterval.Day:
                    return Fix(ts.TotalDays);
                case DateInterval.Hour:
                    return Fix(ts.TotalHours);
                case DateInterval.Minute:
                    return Fix(ts.TotalMinutes);
                    return Fix(ts.TotalSeconds);

        private static long Fix(double Number) {
            if (Number >= 0) {
                return (long)Math.Floor(Number);
            return (long)Math.Ceiling(Number);

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  • Marco Pellicciotta
    30 jan 2014 08:32
    Marco Pellicciotta: After using it a few times a see a bug and I want to report. The fix function must be: private static long Fix(double Number) { if (Number >= 0) { return (long)Math.Ceiling(Number); } return (long)Math.Floor(Number); } } Just change Ceiling by Floor.
  • Marco Pellicciotta
    13 nov 2013 04:46
    The trick is with month values, because TimeSpan do not give you the difference of months.
  • Marco Pellicciotta
    13 nov 2013 04:35
    Exactly what I was looking for. Thanks!
  • Raj
    6 mei 2013 08:48
    If you want the exact DateDiff function as it works in SQL, you can remove time stamp of the Date variables and then Subtract one from another. It will give u exact number of days. Ex. DateTime dt = DateTime.Parse(fromDate.ToShortDateString()); DateTime dt1 = DateTime.Parse(toDate.ToShortDateString()); int noOfDays = dt.Subtract(dt1).TotalDays;

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