C#中按指定时区显示特定格式DateTime及获取对应文化码

Great question! Let's break this down step by step. The short answer: Yes, you can map a time zone to a corresponding culture code, but keep in mind time zones and cultures aren't strictly one-to-one—one time zone might be used by multiple cultures. You'll need to handle that ambiguity based on your business needs.

Let's solve your specific scenario: taking a datetime like 24-02-2018 07:30:00, parsing/displaying it in either DD-MM-YY or MM-DD-YY format based on the target time zone, and integrating this into your email's "Last Updated" field.

Step 1: Convert the DateTime to the Target Time Zone #

First, make sure you're working with a datetime that has clear time zone context (preferably UTC to avoid confusion). Convert it to your target time zone using TimeZoneInfo:

// Example: Original UTC datetime (adjust if your source time is in a different zone)
DateTime utcDateTime = new DateTime(2018, 2, 24, 7, 30, 0, DateTimeKind.Utc);

// Target time zone ID (replace with your actual zone, e.g., "Eastern Standard Time" or "GMT Standard Time")
string targetTimeZoneId = "GMT Standard Time";
TimeZoneInfo targetTimeZone = TimeZoneInfo.FindSystemTimeZoneById(targetTimeZoneId);

// Convert UTC time to the target time zone
DateTime targetDateTime = TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, targetTimeZone);

Step 2: Map Time Zone to a CultureInfo #

A single time zone can be used by multiple cultures (e.g., Eastern Standard Time is used by en-US, es-US, fr-CA). Here's a method to fetch a relevant culture for your time zone, with priority logic to handle ambiguity:

public static CultureInfo GetCultureForTimeZone(string timeZoneId)
{
    TimeZoneInfo targetTimeZone = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);

    // Filter all specific cultures to find those using the target time zone
    var matchingCultures = CultureInfo.GetCultures(CultureTypes.SpecificCultures)
        .Where(culture => 
        {
            try
            {
                var cultureTimeZone = TimeZoneInfo.FindSystemTimeZoneById(culture.DateTimeFormat.TimeZoneId);
                return cultureTimeZone.Id == targetTimeZone.Id;
            }
            catch (TimeZoneNotFoundException)
            {
                // Skip cultures with invalid time zone mappings
                return false;
            }
        })
        .ToList();

    if (!matchingCultures.Any())
    {
        // Fallback to a default culture if no matches are found
        return CultureInfo.InvariantCulture;
        // Or throw an exception if required:
        // throw new InvalidOperationException($"No culture found for time zone: {timeZoneId}");
    }

    // Prioritize a culture that fits your business needs (e.g., English-speaking cultures first)
    return matchingCultures.FirstOrDefault(c => c.Name.StartsWith("en")) ?? matchingCultures.First();
}

Step 3: Format the DateTime for the Target Culture #

Once you have the correct CultureInfo, format the datetime to match the culture's standard pattern, or enforce DD-MM-YY/MM-DD-YY explicitly:

CultureInfo targetCulture = GetCultureForTimeZone(targetTimeZoneId);
string formattedDate;

// Check the culture's short date pattern to decide the format
if (targetCulture.DateTimeFormat.ShortDatePattern.Contains("dd/MM/yy"))
{
    formattedDate = targetDateTime.ToString("dd-MM-yy", targetCulture);
}
else if (targetCulture.DateTimeFormat.ShortDatePattern.Contains("MM/dd/yy"))
{
    formattedDate = targetDateTime.ToString("MM-dd-yy", targetCulture);
}
else
{
    // Fallback to a default format if the culture uses something else
    formattedDate = targetDateTime.ToString("dd-MM-yy", targetCulture);
}

// Combine with time for your email field
string lastUpdatedText = $"最后更新时间：{formattedDate} {targetDateTime.ToString("HH:mm:ss", targetCulture)}";
Console.WriteLine(lastUpdatedText);

Key Notes to Avoid Issues #

• DateTime Kind Matters: Always ensure your source datetime has the correct DateTimeKind (Utc, Local, or Unspecified). Using UTC as your base avoids daylight saving time and offset errors.
• One-to-Many Ambiguity: If a time zone maps to multiple cultures, adjust the GetCultureForTimeZone method to prioritize the culture that makes sense for your users (e.g., use the user's preferred language if available).
• Fallback Logic: Have a fallback culture (like CultureInfo.InvariantCulture) in case no matching culture is found for a time zone.

内容的提问来源于stack exchange，提问作者DevPerson