How to truncate milliseconds off of a .NET DateTime

c# .net datetime
Jeff Putz picture Jeff Putz · Jun 17, 2009 · Viewed 166.7k times · Source

I'm trying to compare a time stamp from an incoming request to a database stored value. SQL Server of course keeps some precision of milliseconds on the time, and when read into a .NET DateTime, it includes those milliseconds. The incoming request to the system, however, does not offer that precision, so I need to simply drop the milliseconds.

I feel like I'm missing something obvious, but I haven't found an elegant way to do it (C#).

Answer

Joe picture Joe · Jun 17, 2009

The following will work for a DateTime that has fractional milliseconds, and also preserves the Kind property (Local, Utc or Undefined).

DateTime dateTime = ... anything ...
dateTime = new DateTime(
    dateTime.Ticks - (dateTime.Ticks % TimeSpan.TicksPerSecond), 
    dateTime.Kind
    );

or the equivalent and shorter:

dateTime = dateTime.AddTicks( - (dateTime.Ticks % TimeSpan.TicksPerSecond));

This could be generalized into an extension method:

public static DateTime Truncate(this DateTime dateTime, TimeSpan timeSpan)
{
    if (timeSpan == TimeSpan.Zero) return dateTime; // Or could throw an ArgumentException
    if (dateTime == DateTime.MinValue || dateTime == DateTime.MaxValue) return dateTime; // do not modify "guard" values
    return dateTime.AddTicks(-(dateTime.Ticks % timeSpan.Ticks));
}

which is used as follows:

dateTime = dateTime.Truncate(TimeSpan.FromMilliseconds(1)); // Truncate to whole ms
dateTime = dateTime.Truncate(TimeSpan.FromSeconds(1)); // Truncate to whole second
dateTime = dateTime.Truncate(TimeSpan.FromMinutes(1)); // Truncate to whole minute
...

Related questions

String was not recognized as a valid DateTime " format dd/MM/yyyy"

I am trying to convert my string formatted value to date type with format dd/MM/yyyy. this.Text="22/11/2009"; DateTime date = DateTime.Parse(this.Text); What is the problem ? It has a second override which asks for IFormatProvider. What is …

Read More
In C#, how do I calculate someone's age based on a DateTime type birthday?

Given a DateTime representing a person's birthday, how do I calculate their age in years?

Read More
Convert UTC/GMT time to local time

We are developing a C# application for a web-service client. This will run on Windows XP PC's. One of the fields returned by the web service is a DateTime field. The server returns a field in GMT format i.e. …

Read More