如何使用区域短日期将 DateTime 转换为字符串

Question

I would like to output a DateTime as a string in the format specified in the operating system preferences. I don't want to provide an explicit format pattern, but instead want to use whatever the user has defined in the Region panel.

For example on my Windows 10 system, formats are defined under Control Panel > Region > Formats as follows:

• Short date: "yyyy-MM-dd"
• Short time: "HH:mm"

When files and folders are displayed in Windows Explorer, they appear in the format: "yyyy-MM-dd HH:mm".

I should point out that I'm using Unity 2019.4.4. -- As far as I know, it's not doing anything strange by overriding the CurrentCulture or anything like that. I've tagged this question with the "unity3d" tag, but it may not be specifically related to Unity, unless Unity is doing strange things with the culture.

I've tried the following .NET Fiddle , and saw the same results as in Unity:

using System;
using System.Globalization;

public class Program
{
    public static void Main()
    {
        long dateTimeTicks = 637314588165245627;
        DateTime dateTime = new DateTime(dateTimeTicks);

        // I thought the following methods might work, since the Region panel allow configuring the
        // short and long formats for date and time.

        Console.WriteLine(dateTime.ToShortDateString());  // 7/27/2020
        Console.WriteLine(dateTime.ToLongDateString());   // Monday, July 27, 2020
        Console.WriteLine(dateTime.ToShortTimeString());  // 3:00 PM
        Console.WriteLine(dateTime.ToLongTimeString());   // 3:00:16 PM

        // None of the standard date and time format strings work. The "o", "s", and "u" are close to
        // what I'm looking for, but I don't want to force this format, I want to use whatever the
        // user has specified in the Region preferences.

        Console.WriteLine(dateTime.ToString());                                // 7/27/2020 3:00:16 PM
        Console.WriteLine(dateTime.ToString(CultureInfo.CurrentCulture));      // 7/27/2020 3:00:16 PM
        Console.WriteLine(dateTime.ToString(CultureInfo.InvariantCulture));    // 07/27/2020 15:00:16
        Console.WriteLine(dateTime.ToString(CultureInfo.InstalledUICulture));  // 7/27/2020 3:00:16 PM

        Console.WriteLine(dateTime.ToString("d"));  // 7/27/2020
        Console.WriteLine(dateTime.ToString("D"));  // Monday, July 27, 2020
        Console.WriteLine(dateTime.ToString("f"));  // Monday, July 27, 2020 3:00 PM
        Console.WriteLine(dateTime.ToString("F"));  // Monday, July 27, 2020 3:00:16 PM
        Console.WriteLine(dateTime.ToString("g"));  // 7/27/2020 3:00 PM
        Console.WriteLine(dateTime.ToString("G"));  // 7/27/2020 3:00:16 PM
        Console.WriteLine(dateTime.ToString("m"));  // July 27
        Console.WriteLine(dateTime.ToString("o"));  // 2020-07-27T15:00:16.5245627
        Console.WriteLine(dateTime.ToString("r"));  // Mon, 27 Jul 2020 15:00:16 GMT
        Console.WriteLine(dateTime.ToString("s"));  // 2020-07-27T15:00:16
        Console.WriteLine(dateTime.ToString("t"));  // 3:00 PM
        Console.WriteLine(dateTime.ToString("T"));  // 3:00:16 PM
        Console.WriteLine(dateTime.ToString("u"));  // 2020-07-27 15:00:16Z
        Console.WriteLine(dateTime.ToString("U"));  // Monday, July 27, 2020 3:00:16 PM
        Console.WriteLine(dateTime.ToString("y"));  // July 2020

        // I considered using CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern and
        // CultureInfo.CurrentCulture.DateTimeFormat.ShortTimePattern together, but they also
        // don't return what is specified in Region preferences.

        // 7/27/2020
        Console.WriteLine(dateTime.ToString(CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern));
    }
}

I'm assuming I need to somehow access the Culture information that's defined in the OS Regions panel and use that to format the string, but that's where I'm lost.

The CurrentCulture seems to be using a ShortDate of "M/d/yyyy" and a ShortTime of "h:mm tt", which is not what I have set in my Region panel.

How can I output the DateTime as a string in the format specified by the user and stored in the Region panel on Windows without knowing what that pattern is ahead of time?

Ultimately, I would like the string to be in the same format used by Windows Explorer, which would be something like "ShortDate ShortTime".

Answer 1

As Martheen stated in the comment, the Unity editor appears to be ignoring or overriding the CurrentCulture as provided by the OS.

---

UPDATE:

I found a solution that does return the data that I'm looking for, which I'll include below. First I'll describe the problem in more detail.

On my Windows 10 system, my Region settings are customized as follows:

• Format: English (United States)
• Short date: "yyyy-MM-dd"
• Short time: "HH:mm"
• Long time: "HH:mm:ss"

The default "en-US" settings for those properties are:

• Format: English (United States)
• Short date: "M/d/yyyy"
• Short time: "h:mm tt"
• Long time: "h:mm:ss tt"

I didn't customize the "Long date" format or any other settings.

Inside Unity, when accessing Thread.CurrentThread.CurrentCulture , it does seem to return the proper culture, but in its default state. It's as if when Unity loads, it sees that "en-US" is being used, but it then overwrites the culture with default values. Something like this:

var culture = Thread.CurrentThread.CurrentCulture;
Thread.CurrentThread.CurrentCulture = new CultureInfo(culture.Name);

Later, when trying to get the short date and time formats, they return the default values instead of the values I've specified in Region settings.

var culture = Thread.CurrentThread.CurrentCulture;
string shortDatePattern = culture.DateTimeFormat.ShortDatePattern; // "M/d/yyyy"
string shortTimePattern = culture.DateTimeFormat.ShortTimePattern; // "h:mm tt"

By invoking the GetLocaleInfoEx() method included in kernel32.dll and passing certain parameters, I can access the actual Region settings active on my system. The following methods can return the format pattern for the short date, short time, and long time. And GetDateTimeFormat() returns for me the combined short date and long time for the current culture: "yyyy-MM-dd HH:mm:ss".

public class LocaleFunctions
{
   public enum LCTYPE : uint
   {
      // There are 150+ values than can be passed to GetLocaleInfoEx(),
      // but most were excluded for brevity.
      //
      // See the following header file for defines with the "LOCALE_" prefix:
      //    https://github.com/wine-mirror/wine/blob/master/include/winnls.h
      //
      LOCALE_SSHORTDATE = 0x001F,
      LOCALE_STIMEFORMAT = 0x1003,
      LOCALE_SSHORTTIME = 0x0079
   }

   public static string GetDateTimeFormat()
   {
      var locale = Thread.CurrentThread.CurrentCulture.Name;
      return GetShortDateFormat(locale) + " " + GetLongTimeFormat(locale);
   }

   public static string GetLongTimeFormat(string locale, int maxLength = 32)
   {
      var data = new StringBuilder(maxLength);
      GetLocaleInfoEx(locale, LCTYPE.LOCALE_STIMEFORMAT, data, maxLength);
      return data.ToString();
   }

   public static string GetShortDateFormat(string locale, int maxLength = 32)
   {
      var data = new StringBuilder(maxLength);
      GetLocaleInfoEx(locale, LCTYPE.LOCALE_SSHORTDATE, data, maxLength);
      return data.ToString();
   }

   public static string GetShortTimeFormat(string locale, int maxLength = 32)
   {
      var data = new StringBuilder(maxLength);
      GetLocaleInfoEx(locale, LCTYPE.LOCALE_SSHORTTIME, data, maxLength);
      return data.ToString();
   }

   // pInvoke declarations
   [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
   private static extern int GetLocaleInfoEx(
      string lpLocaleName,
      LCTYPE lcType,
      StringBuilder lpLCData,
      int cchData);
}

Answer 2

It seems that Unity can't get the values directly from the Operating System, but you can still formatting your DateTime as shown below, with all the system options:

    System.DateTime currentTime = System.DateTime.Now;

    void Start()
    {
        //Short date
        Debug.Log(currentTime.ToString("M/d/yyyy"));
        Debug.Log(currentTime.ToString("M/d/yy"));
        Debug.Log(currentTime.ToString("MM/dd/yy"));
        Debug.Log(currentTime.ToString("MM/dd/yyyy"));
        Debug.Log(currentTime.ToString("yy/MM/dd"));
        Debug.Log(currentTime.ToString("yyyy-MM-dd"));
        Debug.Log(currentTime.ToString("dd-MMM-yy"));

        //Long date
        Debug.Log(currentTime.ToString("dddd, MMMM d, yyyy"));
        Debug.Log(currentTime.ToString("MMMM d, yyyy"));
        Debug.Log(currentTime.ToString("dddd, d MMMM, yyyy"));
        Debug.Log(currentTime.ToString("d MMMM, yyyy"));

        //Short time
        Debug.Log(currentTime.ToString("h:mm tt"));
        Debug.Log(currentTime.ToString("hh:mm tt"));
        Debug.Log(currentTime.ToString("H:mm"));
        Debug.Log(currentTime.ToString("HH:mm"));

        //Long time
        Debug.Log(currentTime.ToString("h:mm:ss tt"));
        Debug.Log(currentTime.ToString("hh:mm:ss t"));
        Debug.Log(currentTime.ToString("H:mm:ss"));
        Debug.Log(currentTime.ToString("HH:mm:ss"));
    }