What about MONTHS!!!!!!

Meant to say... this is to simplistic - there are more than 365 days in a year every so often according to that rule!

其實本來就不應該計算 Year 和 Month 的 DateDiff, 因為 Year 和 Month 是不固定長度的，我想這也是 C# 的 TimeSpan 只做到 TotalDays 的原因吧~

Um, why not use DateDiff itself?

Add a reference to Microsoft.VisualBasic, add:

using Microsoft.VisualBasic;

(form w/ three textboxes & a button)

private void button1_Click(object sender, System.EventArgs e)
{
DateTime FromDate;
DateTime ToDate;
FromDate = DateTime.Parse(this.textBox1.Text);
ToDate = DateTime.Parse(this.textBox2.Text);

this.textBox3.Text = DateAndTime.DateDiff (DateInterval.Month, FromDate,ToDate, FirstDayOfWeek.System, FirstWeekOfYear.System ).ToString();
}

The only bummer is C#'s lack of support for Optional parameters, so you have to code FirstDayOfWeek.System & FirstWeekOfYear.System as the last two parameters. (A little confusing if you're used to VB :-)

Here's a little trick I found. Die-Hard C#'ers will probably yell and scream at me for this, but oh well...

public static double DateDiff(string Interval, DateTime startDate, DateTime endDate)
{
return Microsoft.VisualBasic.DateAndTime.DateDiff(Interval, startDate, endDate, Microsoft.VisualBasic.FirstDayOfWeek.System, Microsoft.VisualBasic.FirstWeekOfYear.System);
}

hi
that code is realy good

thanx

why not use TimeSpan.Subtract

Yep, the timespan subtract is the easiest approach.

TimeSpan dateDiff = dtEnd - dtStart; //returns the difference in days

ok~

不错~

Try using this. The code is really one line and is only to return the difference in months. You can test this in excel if you wish.

/// <summary>
/// Returns the number of months between startDate and endDate.
/// If the startDate is less than endDate the result is negative.
/// </summary>
/// <param name="startDate">Start Date</param>
/// <param name="endDate">End Date</param>
/// <returns></returns>
public int MonthDifference(DateTime startDate, DateTime endDate)
{
#region Analysis
// This came from the following analysis
// Assume 1 is start date and 2 is end date
// if Y2 = Y1 then M2 - M1
// else (12 - M1) + [(Y2 - Y1 - 1) * 12] + M2
#endregion

return endDate.Month - startDate.Month + ((endDate.Year - startDate.Year) * 12);
}

Correction. Code documentation should read If <b>startDate is greated than endDate</b> (not less)
Thanks

new TimeSpan(date_1.Ticks - date_2.Ticks).Days
returns days

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It’s very good article. Great site with very good look and perfect information.

Yep, the timespan subtract is the easiest approach.

Interesting article!
Thanks

Thanks for help, Keep up the good work.

Keep up the good work.

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Timespan works great for days, but what about months?!! It's not posible to calculate the difference using timespan if you are looking for the difference in months. Sorry, it is possible, but there will be a lot of crazy code to check each month to see what the last day of the month is (not very efficient).