Have datetime.now return to the nearest second

Question

I have a \"requirement\" to give a timestamp to the nearest second... but NOT more accurate than that. Rounding or truncating the time is fine.

I have come up with t

Answer 1

After working with the selected solution I am satisfied that it works well. However the implementations of the extension methods posted here do not offer any validation to ensure the ticks value you pass in is a valid ticks value. They also do not preserve the DateTimeKind of the DateTime object being truncated. (This has subtle but relevant side effects when storing to a database like MongoDB.)

If the true goal is to truncate a DateTime to a specified value (i.e. Hours/Minutes/Seconds/MS) I recommend implementing this extension method in your code instead. It ensures that you can only truncate to a valid precision and it preserves the important DateTimeKind metadata of your original instance:

public static DateTime Truncate(this DateTime dateTime, long ticks)
{
    bool isValid = ticks == TimeSpan.TicksPerDay 
        || ticks == TimeSpan.TicksPerHour 
        || ticks == TimeSpan.TicksPerMinute 
        || ticks == TimeSpan.TicksPerSecond 
        || ticks == TimeSpan.TicksPerMillisecond;

    // https://stackoverflow.com/questions/21704604/have-datetime-now-return-to-the-nearest-second
    return isValid 
        ? DateTime.SpecifyKind(
            new DateTime(
                dateTime.Ticks - (dateTime.Ticks % ticks)
            ),
            dateTime.Kind
        )
        : throw new ArgumentException("Invalid ticks value given. Only TimeSpan tick values are allowed.");
}

Then you can use the method like this:

DateTime dateTime = DateTime.UtcNow.Truncate(TimeSpan.TicksPerMillisecond);

dateTime.Kind => DateTimeKind.Utc