How to determine if current culture/locale uses am/pm or 24-hour time?

Question

I need to determine if the current culture/locale is set to use am/pm time or 24-hour time.

At first I thought I could do this:

bool time24Hour = Thread.CurrentThread.CurrentCulture.DateTimeFormat.AMDesignator == "";

But then I read the comments on the last answer on this thread Get just the hour of day from DateTime using either 12 or 24 hour format as defined by the current culture which seems to imply this won't work.

I guess I could format an arbitrary time, and then analyze the results, but surely there's a simplier way?

EDIT:

See also my comment below - I just want to determine which one of two pre-formatted constant strings containing lists of hours I should select, and hope to avoid a lot of unnecessary contortions - I just need a yes/no answer as to whether this is an am/pm culture or a 24-hour culture.

The program is a WinForms program, if that is of any help.

I need to select one of two pre-generated and constant lists of hours, either "9 10 11 12 13 14 15 16 17" or "9 10 11 12 1 2 3 4 5", depending on the culture. I'm hoping it isn't necessary to go through a lot of contortions involving DateTime and formatting and so on. — RenniePet, Sep 05 '11 at 00:09
First, you should edit your question to include that information. Second, are you using Windows Forms? Web Forms? Silverlight? — John Saunders, Sep 05 '11 at 00:11

dario_ramos · Accepted Answer · 2011-09-05T16:52:33.383

11

Try checking if DateTimeFormat.ShortTimePattern contains H. If it does, the system is using 24-hour time

edited Sep 05 '11 at 16:52

answered Sep 05 '11 at 02:20

dario_ramos

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Thanks, that looks like the proper approach. But wouldn't it be even more correct to test for just "H"? (Or "HH", but that would be redundant.) – RenniePet Sep 05 '11 at 12:02
One other very minor point - I can see you added WinForms as a tag for my question, but isn't my question and your answer independent of the presentation system being used? – RenniePet Sep 05 '11 at 12:04
1) You're right, I edited my answer 2) I did it just because you said you're doing it in Winforms. Not sure if Silverlight and WPF have a different way of doing this. – dario_ramos Sep 05 '11 at 16:51
what about checking for Contains("t") – Omu Dec 13 '14 at 15:52

score 3 · Answer 2 · answered Jun 10 '13 at 11:02

Just a small addition if I may. Based on the answer by dario_ramos, I turned this into an extension method with a supporting unit test, which passes on my system (checking 378 cultures).

public static class DateTimeExtensions
{
    public static bool Is24Hrs(this CultureInfo cultureInfo)
    {
        return cultureInfo.DateTimeFormat.ShortTimePattern.Contains("H");
    }
}

[TestClass]
public class DateTimeExtensionTests
{
    [TestMethod]
    public void Unit_Can_Determine_If_Culture_Uses_24HrTime()
    {
        var cultures = CultureInfo.GetCultures(CultureTypes.AllCultures);
        foreach (var cultureInfo in cultures)
        {
            Thread.CurrentThread.CurrentCulture = cultureInfo;
            var datetime = new DateTime(2000, 1, 1, 23, 0, 0);
            var formatted = datetime.ToString("t");
            var is24Hrs = formatted.Contains("23");
            Assert.AreEqual(is24Hrs, cultureInfo.Is24Hrs());
        }
    }
}

How to determine if current culture/locale uses am/pm or 24-hour time?

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