What cultures use 24 hour time? (example limits to english cultures) from stack overflow answer...

24 hour cultures

void Main()
{
  var cultures = System.Globalization.CultureInfo.GetCultures(System.Globalization.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());
    if (cultureInfo.TwoLetterISOLanguageName == "en")
      (cultureInfo.NativeName + " " + is24Hrs.ToString() + " " + cultureInfo.Is24Hrs()).Dump();
  }
}

// Define other methods and classes here
public static class DateTimeExtensions
{
  public static bool Is24Hrs(this System.Globalization.CultureInfo cultureInfo)
  {
    return cultureInfo.DateTimeFormat.ShortTimePattern.Contains("H");
  }
}

This is setup to run in LinqPad