Question

I need to change/update/set my system (windows7) default dateTime format programatically and permanently until I change it myself through code or through windows GUI

I have tried a lot of solutions like this one from Code Project

       Console.Write(DateTime.Now + "");
       RegistryKey rkey = Registry.CurrentUser.OpenSubKey(@"
       Control Panel\International", true);
        rkey.SetValue("sShortDate", "dd/MM/yyyy");
        rkey.SetValue("sLongDate", "dd/MM/yyyy");
       Console.Write(DateTime.Now + "");

The closest and well reputed answer is following from from Set Default DateTime Format c#, I tried this solution but it did not help me. As It does not change my system datetime format (shown in taskbar). And after I restart the app having this code, I again get the old format before this code is executed.

using System;
using System.Globalization;
using System.Threading;

namespace test 
{
    public static class Program
    {
        public static void Main() {
          Console.Write(DateTime.Now + "");// MessageBox.Show(DateTime.Now + "");
          CultureInfo culture = (CultureInfo)CultureInfo.CurrentCulture.Clone();
          culture.DateTimeFormat.ShortDatePattern = "dd-MMM-yyyy";
          culture.DateTimeFormat.LongTimePattern = "";
          Thread.CurrentThread.CurrentCulture = culture;
          Console.Write(DateTime.Now + "");// MessageBox.Show(DateTime.Now + "");
        }
    }
}

Answer 1

I tried manually changing the registry keys mentioned in your question.

Here’s what I did:

• Pressed Win+R and type ‘regedit’ to get the Registry Editor.
• Navigated the tree to Computer → HKEY_CURRENT_USER → Control Panel → International.
• Double clicked the ‘sShortDate’ entry and changed the value to ‘yyyy/MM/dd’.

I then opened Windows Explorer and all of the dates were shown in the new format, so this is definitely the right place in the registry.

I then tried the code you supplied to modify the registry and it, too, is changing the date shown in Explorer.

So, this leads me to believe that the Windows taskbar clock does not react to changes to this setting. I confirmed this by killing and restarting ‘explorer.exe’ from the Task Manager. If you restart Explorer you too should see the change take effect.

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Edit: there appears to be no facility in .NET for setting the locale settings directly. You can, however, use P/Invoke to set it via the C++ Win API which should then cause the system clock (and other applications) to be notified of the change. See this discussion.