Format RSS pubDate as .NET DateTime

I have an implementation of the RSS 822 DateTime format as a an answer to the question "How do I parse and convert DateTime’s to the RFC-822 date-time format that should solve your problem.

This is an implementation in C# of how to parse and convert a DateTime to and from its RFC-822 representation. The only restriction it has is that the DateTime is in Coordinated Universal Time (UTC).

/// <summary>/// Provides methods for converting <see cref="DateTime"/> structures /// to and from the equivalent <a href="http://www.w3.org/Protocols/rfc822/#z28">RFC 822</a> /// string representation./// </summary>public class Rfc822DateTime{    //============================================================    //  Private members    //============================================================    #region Private Members    /// <summary>    /// Private member to hold array of formats that RFC 822 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 822 format.    /// </summary>    private const string format     = "ddd, dd MMM yyyy HH:mm:ss K";    #endregion    //============================================================    //  Public Properties    //============================================================    #region Rfc822DateTimeFormat    /// <summary>    /// Gets the custom format specifier that may be used to represent a <see cref="DateTime"/> in the RFC 822 format.    /// </summary>    /// <value>A <i>DateTime format string</i> that may be used to represent a <see cref="DateTime"/> in the RFC 822 format.</value>    /// <remarks>    /// <para>    /// This method returns a string representation of a <see cref="DateTime"/> that utilizes the time zone     /// offset (local differential) to represent the offset from Greenwich mean time in hours and minutes.     /// The <see cref="Rfc822DateTimeFormat"/> is a valid date-time format string for use     /// in the <see cref="DateTime.ToString(String, IFormatProvider)"/> method.    /// </para>    /// <para>    /// The <a href="http://www.w3.org/Protocols/rfc822/#z28">RFC 822</a> Date and Time specification     /// specifies that the year will be represented as a two-digit value, but the     /// <a href="http://www.rssboard.org/rss-profile#data-types-datetime">RSS Profile</a> recommends that     /// all date-time values should use a four-digit year. The <see cref="Rfc822DateTime"/> class     /// follows the RSS Profile recommendation when converting a <see cref="DateTime"/> to the equivalent     /// RFC 822 string representation.    /// </para>    /// </remarks>    public static string Rfc822DateTimeFormat    {        get        {            return format;        }    }    #endregion    #region Rfc822DateTimePatterns    /// <summary>    /// Gets an array of the expected formats for RFC 822 date-time string representations.    /// </summary>    /// <value>    /// An array of the expected formats for RFC 822 date-time string representations     /// that may used in the <see cref="DateTime.TryParseExact(String, string[], IFormatProvider, DateTimeStyles, out DateTime)"/> method.    /// </value>    /// <remarks>    /// The array of the expected formats that is returned assumes that the RFC 822 time zone     /// is represented as or converted to a local differential representation.    /// </remarks>    /// <seealso cref="ConvertZoneToLocalDifferential(String)"/>    public static string[] Rfc822DateTimePatterns    {        get        {            if (formats.Length > 0)            {                return formats;            }            else            {                formats = new string[35];                // two-digit day, four-digit year patterns                formats[0]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'fffffff zzzz";                formats[1]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'ffffff zzzz";                formats[2]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'fffff zzzz";                formats[3]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'ffff zzzz";                formats[4]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'fff zzzz";                formats[5]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'ff zzzz";                formats[6]  = "ddd',' dd MMM yyyy HH':'mm':'ss'.'f zzzz";                formats[7]  = "ddd',' dd MMM yyyy HH':'mm':'ss zzzz";                // two-digit day, two-digit year patterns                formats[8]  = "ddd',' dd MMM yy HH':'mm':'ss'.'fffffff zzzz";                formats[9]  = "ddd',' dd MMM yy HH':'mm':'ss'.'ffffff zzzz";                formats[10] = "ddd',' dd MMM yy HH':'mm':'ss'.'fffff zzzz";                formats[11] = "ddd',' dd MMM yy HH':'mm':'ss'.'ffff zzzz";                formats[12] = "ddd',' dd MMM yy HH':'mm':'ss'.'fff zzzz";                formats[13] = "ddd',' dd MMM yy HH':'mm':'ss'.'ff zzzz";                formats[14] = "ddd',' dd MMM yy HH':'mm':'ss'.'f zzzz";                formats[15] = "ddd',' dd MMM yy HH':'mm':'ss zzzz";                // one-digit day, four-digit year patterns                formats[16] = "ddd',' d MMM yyyy HH':'mm':'ss'.'fffffff zzzz";                formats[17] = "ddd',' d MMM yyyy HH':'mm':'ss'.'ffffff zzzz";                formats[18] = "ddd',' d MMM yyyy HH':'mm':'ss'.'fffff zzzz";                formats[19] = "ddd',' d MMM yyyy HH':'mm':'ss'.'ffff zzzz";                formats[20] = "ddd',' d MMM yyyy HH':'mm':'ss'.'fff zzzz";                formats[21] = "ddd',' d MMM yyyy HH':'mm':'ss'.'ff zzzz";                formats[22] = "ddd',' d MMM yyyy HH':'mm':'ss'.'f zzzz";                formats[23] = "ddd',' d MMM yyyy HH':'mm':'ss zzzz";                // two-digit day, two-digit year patterns                formats[24] = "ddd',' d MMM yy HH':'mm':'ss'.'fffffff zzzz";                formats[25] = "ddd',' d MMM yy HH':'mm':'ss'.'ffffff zzzz";                formats[26] = "ddd',' d MMM yy HH':'mm':'ss'.'fffff zzzz";                formats[27] = "ddd',' d MMM yy HH':'mm':'ss'.'ffff zzzz";                formats[28] = "ddd',' d MMM yy HH':'mm':'ss'.'fff zzzz";                formats[29] = "ddd',' d MMM yy HH':'mm':'ss'.'ff zzzz";                formats[30] = "ddd',' d MMM yy HH':'mm':'ss'.'f zzzz";                formats[31] = "ddd',' d MMM yy HH':'mm':'ss zzzz";                // Fall back patterns                formats[32] = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'fffffffK"; // RoundtripDateTimePattern                formats[33] = DateTimeFormatInfo.InvariantInfo.UniversalSortableDateTimePattern;                formats[34] = 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"/>,     /// expressed as <i>Coordinated Universal Time (UTC)</i>.    /// </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="ArgumentNullException"><paramref name="s"/> is an empty string.</exception>    /// <exception cref="FormatException"><paramref name="s"/> does not contain a valid RFC 822 string representation of a date and time.</exception>    public static DateTime Parse(string s)    {        //------------------------------------------------------------        //  Validate parameter        //------------------------------------------------------------        Guard.ArgumentNotNullOrEmptyString(s, "s");        DateTime result;        if (Rfc822DateTime.TryParse(s, out result))        {            return result;        }        else        {            throw new FormatException(String.Format(null, "{0} is not a valid RFC 822 string representation of a date and time.", s));        }    }    #endregion    #region ConvertZoneToLocalDifferential(string s)    /// <summary>    /// Converts the time zone component of an RFC 822 date and time string representation to its local differential (time zone offset).    /// </summary>    /// <param name="s">A string containing an RFC 822 date and time to convert.</param>    /// <returns>A date and time string that uses local differential to describe the time zone equivalent to the date and time contained in <paramref name="s"/>.</returns>    /// <exception cref="ArgumentNullException"><paramref name="s"/> is a <b>null</b> reference (Nothing in Visual Basic).</exception>    /// <exception cref="ArgumentNullException"><paramref name="s"/> is an empty string.</exception>    public static string ConvertZoneToLocalDifferential(string s)    {        string zoneRepresentedAsLocalDifferential   = String.Empty;        //------------------------------------------------------------        //  Validate parameter        //------------------------------------------------------------        Guard.ArgumentNotNullOrEmptyString(s, "s");        if(s.EndsWith(" UT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" UT") + 1) ), "+00:00");        }        else if (s.EndsWith(" GMT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" GMT") + 1 ) ), "+00:00");        }        else if (s.EndsWith(" EST", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" EST") + 1)), "-05:00");        }        else if (s.EndsWith(" EDT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" EDT") + 1)), "-04:00");        }        else if (s.EndsWith(" CST", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" CST") + 1)), "-06:00");        }        else if (s.EndsWith(" CDT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" CDT") + 1)), "-05:00");        }        else if (s.EndsWith(" MST", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" MST") + 1)), "-07:00");        }        else if (s.EndsWith(" MDT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" MDT") + 1)), "-06:00");        }        else if (s.EndsWith(" PST", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" PST") + 1)), "-08:00");        }        else if (s.EndsWith(" PDT", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" PDT") + 1)), "-07:00");        }        else if (s.EndsWith(" Z", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" Z") + 1)), "+00:00");        }        else if (s.EndsWith(" A", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" A") + 1)), "-01:00");        }        else if (s.EndsWith(" M", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" M") + 1)), "-12:00");        }        else if (s.EndsWith(" N", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" N") + 1)), "+01:00");        }        else if (s.EndsWith(" Y", StringComparison.OrdinalIgnoreCase))        {            zoneRepresentedAsLocalDifferential  = String.Concat(s.Substring(0, (s.LastIndexOf(" Y") + 1)), "+12:00");        }        else        {            zoneRepresentedAsLocalDifferential  = s;        }        return zoneRepresentedAsLocalDifferential;    }    #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 822 string representation of the value of the <paramref name="utcDateTime"/>.</returns>    /// <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(Rfc822DateTime.Rfc822DateTimeFormat, 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"/>, expressed as <i>Coordinated Universal Time (UTC)</i>,     /// 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(Rfc822DateTime.ConvertZoneToLocalDifferential(s), Rfc822DateTime.Rfc822DateTimePatterns, DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AdjustToUniversal, out parseResult))            {                result          = DateTime.SpecifyKind(parseResult, DateTimeKind.Utc);                wasConverted    = true;            }        }        return wasConverted;    }    #endregion }

it is better to useDateTime.Now.Tostring("r") instead

Something close to this should work:

string orig = "Wed, 29 Oct 2008 14:14:48 +0000";string newstring = String.Format("{0:MM/dd/yyyy hh:mm tt}", DateTime.Parse(orig.Remove(orig.IndexOf(" +"))));

Taken from http://blog.stevex.net/index.php/string-formatting-in-csharp/