DateTimeを解析してRFC 3339の日付/時刻形式に変換するにはどうすればよいですか？

Question

DateTime構造体を対応するRFC 3339形式の文字列表現に変換したり、この文字列表現を解析してDateTime構造に戻したりするにはどうすればよいですか？ RFC-3339日時フォーマットは、Atom Syndication Formatなどの多くの仕様で使用されています。

Answer 1

これは、RFC-3339表現との間でDateTimeを解析および変換する方法をC＃で実装したものです。それが持つ唯一の制限は、DateTimeが協定世界時（UTC）であることです。 .NETで

using System; 
using System.Globalization; 

namespace DateTimeConsoleApplication 
{ 
    /// <summary> 
    /// Provides methods for converting <see cref="DateTime"/> structures to and from the equivalent RFC 3339 string representation. 
    /// </summary> 
    public static class Rfc3339DateTime 
    { 
     //============================================================ 
     // Private members 
     //============================================================ 
     #region Private Members 
     /// <summary> 
     /// Private member to hold array of formats that RFC 3339 date-time representations conform to. 
     /// </summary> 
     private static string[] formats = new string[0]; 
     /// <summary> 
     /// Private member to hold the DateTime format string for representing a DateTime in the RFC 3339 format. 
     /// </summary> 
     private const string format = "yyyy-MM-dd'T'HH:mm:ss.fffK"; 
     #endregion 

     //============================================================ 
     // Public Properties 
     //============================================================ 
     #region Rfc3339DateTimeFormat 
     /// <summary> 
     /// Gets the custom format specifier that may be used to represent a <see cref="DateTime"/> in the RFC 3339 format. 
     /// </summary> 
     /// <value>A <i>DateTime format string</i> that may be used to represent a <see cref="DateTime"/> in the RFC 3339 format.</value> 
     /// <remarks> 
     /// <para> 
     /// This method returns a string representation of a <see cref="DateTime"/> that 
     /// is precise to the three most significant digits of the seconds fraction; that is, it represents 
     /// the milliseconds in a date and time value. The <see cref="Rfc3339DateTimeFormat"/> is a valid 
     /// date-time format string for use in the <see cref="DateTime.ToString(String, IFormatProvider)"/> method. 
     /// </para> 
     /// </remarks> 
     public static string Rfc3339DateTimeFormat 
     { 
      get 
      { 
       return format; 
      } 
     } 
     #endregion 

     #region Rfc3339DateTimePatterns 
     /// <summary> 
     /// Gets an array of the expected formats for RFC 3339 date-time string representations. 
     /// </summary> 
     /// <value> 
     /// An array of the expected formats for RFC 3339 date-time string representations 
     /// that may used in the <see cref="DateTime.TryParseExact(String, string[], IFormatProvider, DateTimeStyles, out DateTime)"/> method. 
     /// </value> 
     public static string[] Rfc3339DateTimePatterns 
     { 
      get 
      { 
       if (formats.Length > 0) 
       { 
        return formats; 
       } 
       else 
       { 
        formats = new string[11]; 

        // Rfc3339DateTimePatterns 
        formats[0] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffffffK"; 
        formats[1] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'ffffffK"; 
        formats[2] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffffK"; 
        formats[3] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'ffffK"; 
        formats[4] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffK"; 
        formats[5] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'ffK"; 
        formats[6] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fK"; 
        formats[7] = "yyyy'-'MM'-'dd'T'HH':'mm':'ssK"; 

        // Fall back patterns 
        formats[8] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffffffK"; // RoundtripDateTimePattern 
        formats[9] = DateTimeFormatInfo.InvariantInfo.UniversalSortableDateTimePattern; 
        formats[10] = DateTimeFormatInfo.InvariantInfo.SortableDateTimePattern; 

        return formats; 
       } 
      } 
     } 
     #endregion 

     //============================================================ 
     // Public Methods 
     //============================================================ 
     #region Parse(string s) 
     /// <summary> 
     /// Converts the specified string representation of a date and time to its <see cref="DateTime"/> equivalent. 
     /// </summary> 
     /// <param name="s">A string containing a date and time to convert.</param> 
     /// <returns>A <see cref="DateTime"/> equivalent to the date and time contained in <paramref name="s"/>.</returns> 
     /// <remarks> 
     /// The string <paramref name="s"/> is parsed using formatting information in the <see cref="DateTimeFormatInfo.InvariantInfo"/> object. 
     /// </remarks> 
     /// <exception cref="ArgumentNullException"><paramref name="s"/> is a <b>null</b> reference (Nothing in Visual Basic).</exception> 
     /// <exception cref="FormatException"><paramref name="s"/> does not contain a valid RFC 3339 string representation of a date and time.</exception> 
     public static DateTime Parse(string s) 
     { 
      //------------------------------------------------------------ 
      // Validate parameter 
      //------------------------------------------------------------ 
      if(s == null) 
      { 
       throw new ArgumentNullException("s"); 
      } 

      DateTime result; 
      if (Rfc3339DateTime.TryParse(s, out result)) 
      { 
       return result; 
      } 
      else 
      { 
       throw new FormatException(String.Format(null, "{0} is not a valid RFC 3339 string representation of a date and time.", s)); 
      } 
     } 
     #endregion 

     #region ToString(DateTime utcDateTime) 
     /// <summary> 
     /// Converts the value of the specified <see cref="DateTime"/> object to its equivalent string representation. 
     /// </summary> 
     /// <param name="utcDateTime">The Coordinated Universal Time (UTC) <see cref="DateTime"/> to convert.</param> 
     /// <returns>A RFC 3339 string representation of the value of the <paramref name="utcDateTime"/>.</returns> 
     /// <remarks> 
     /// <para> 
     /// This method returns a string representation of the <paramref name="utcDateTime"/> that 
     /// is precise to the three most significant digits of the seconds fraction; that is, it represents 
     /// the milliseconds in a date and time value. 
     /// </para> 
     /// <para> 
     /// While it is possible to display higher precision fractions of a second component of a time value, 
     /// that value may not be meaningful. The precision of date and time values depends on the resolution 
     /// of the system clock. On Windows NT 3.5 and later, and Windows Vista operating systems, the clock's 
     /// resolution is approximately 10-15 milliseconds. 
     /// </para> 
     /// </remarks> 
     /// <exception cref="ArgumentException">The specified <paramref name="utcDateTime"/> object does not represent a <see cref="DateTimeKind.Utc">Coordinated Universal Time (UTC)</see> value.</exception> 
     public static string ToString(DateTime utcDateTime) 
     { 
      if (utcDateTime.Kind != DateTimeKind.Utc) 
      { 
       throw new ArgumentException("utcDateTime"); 
      } 

      return utcDateTime.ToString(Rfc3339DateTime.Rfc3339DateTimeFormat, DateTimeFormatInfo.InvariantInfo); 
     } 
     #endregion 

     #region TryParse(string s, out DateTime result) 
     /// <summary> 
     /// Converts the specified string representation of a date and time to its <see cref="DateTime"/> equivalent. 
     /// </summary> 
     /// <param name="s">A string containing a date and time to convert.</param> 
     /// <param name="result"> 
     /// When this method returns, contains the <see cref="DateTime"/> value equivalent to the date and time 
     /// contained in <paramref name="s"/>, if the conversion succeeded, 
     /// or <see cref="DateTime.MinValue">MinValue</see> if the conversion failed. 
     /// The conversion fails if the s parameter is a <b>null</b> reference (Nothing in Visual Basic), 
     /// or does not contain a valid string representation of a date and time. 
     /// This parameter is passed uninitialized. 
     /// </param> 
     /// <returns><b>true</b> if the <paramref name="s"/> parameter was converted successfully; otherwise, <b>false</b>.</returns> 
     /// <remarks> 
     /// The string <paramref name="s"/> is parsed using formatting information in the <see cref="DateTimeFormatInfo.InvariantInfo"/> object. 
     /// </remarks> 
     public static bool TryParse(string s, out DateTime result) 
     { 
      //------------------------------------------------------------ 
      // Attempt to convert string representation 
      //------------------------------------------------------------ 
      bool wasConverted = false; 
      result    = DateTime.MinValue; 

      if (!String.IsNullOrEmpty(s)) 
      { 
       DateTime parseResult; 
       if (DateTime.TryParseExact(s, Rfc3339DateTime.Rfc3339DateTimePatterns, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AdjustToUniversal, out parseResult)) 
       { 
        result   = DateTime.SpecifyKind(parseResult, DateTimeKind.Utc); 
        wasConverted = true; 
       } 
      } 

      return wasConverted; 
     } 
     #endregion 
    } 
} 

Answer 2

（UTCを想定）：

datetime.ToString("YYYY-MM-DD'T'HH:mm:ssZ") 

DateTime.Parse()バックDateTime構造に変換するために使用することができます。

Answer 3

独自のコンバージョンコードを書く必要はありません。ただ、RFC-3339の文字列を解析するために

XmlConvert.ToDateTime(string s, XmlDateTimeSerializationMode dateTimeOption) 

を使用し、

XmlConvert.ToString(DateTime value, XmlDateTimeSerializationMode dateTimeOption) 

は、文字列に（UTC）日時を変換します。

Ref。
http://msdn.microsoft.com/en-us/library/ms162342(v=vs.110).aspx
http://msdn.microsoft.com/en-us/library/ms162344(v=vs.110).aspx

Answer 4

簡単な式はあなたが結果を得ることができた後になります。

rfcFormat = DateDiff("s", "1/1/1970", Now())