Paul,
I wish I could remember where this code is actually from. I've searched and
can't find/remember the website. But it's from a gentleman who wrote an rss
feed aggregator. His biggest complaint was the lack of a standardized date
between types of feeds. Part of his code was this date class which he uses
to standardize the dates (He gives it away free and says it's ok to modify
so I'm posting it here. I'm going to keep searching for the site he put it
out on):
Imports Microsoft.VisualBasic
Namespace RssComponents
Public Class DateTimeExt
Private Shared regExpression As String =
"\s*(?
?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)" & _
"\s*,\s*)?(\d{1,2})\s+(Jan|Feb|Mar|Apr|May|Jun" & _
"|Jul|Aug|Sep|Oct|Nov|Dec)\s+(\d{2,})\s+(\d{2})\s*:\s*(\d{2})\s*(?::\s*(\d{2}))?"
& _
"\s+([+\-]\d{4}|UT|GMT|EST|EDT|CST|CDT|MST|MDT|PST|PDT|[A-IK-Z])"
Private Shared rfc2822 As Regex = New Regex(regExpression,
RegexOptions.Compiled)
Private Shared months As New ArrayList(New String() _
{"ZeroIndex", "Jan", "Feb", "Mar", "Apr", "May", "Jun", _
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"})
'private static TimeSpan dayLightDelta =
TimeZone.CurrentTimeZone.GetDaylightChanges(DateTime.Now.Year).Delta
''' <summary>
''' Converts an ISO 8601 date to a DateTime object. Helper method
needed to
''' deal with timezone offset since they are unsupported by the
''' .NET Framework.
''' </summary>
''' <param name="datetime">DateTime string</param>
''' <returns>DateTime instance</returns>
''' <exception cref="FormatException">On format errors parsing the
datetime</exception>
Public Shared Function ToDateTime(ByVal datetime As String) As
DateTime
Dim timeIndex As Integer = datetime.IndexOf(":")
If timeIndex <> -1 Then
Dim tzoneIndex As Integer = datetime.IndexOf("-", timeIndex)
If tzoneIndex = -1 Then
tzoneIndex = datetime.IndexOf("+", timeIndex)
If tzoneIndex <> -1 Then 'timezone is ahead of UTC
Return AddOffset("+", datetime, tzoneIndex)
End If
Else 'timezone is behind UTC
Return AddOffset("-", datetime, tzoneIndex)
End If
End If
Return System.Xml.XmlConvert.ToDateTime(datetime,
"yyyy-MM-ddTHH:mm:sszzzzzz")
End Function
''' <summary>
''' Parse is able to parse RFC2822/RFC822 formatted dates.
''' It has a fallback mechanism: if the string does not match,
''' the normal DateTime.Parse() function is called.
''' </summary>
''' <param name="dateTimeString">DateTime String to parse</param>
''' <returns>DateTime instance</returns>
''' <exception cref="FormatException">On format errors parsing the
datetime</exception>
Public Shared Function Parse(ByVal dateTimeString As String) As
DateTime
If dateTimeString = Nothing Then
Return DateTime.Now.ToUniversalTime()
End If
If dateTimeString.Trim().Length = 0 Then
Return DateTime.Now.ToUniversalTime()
End If
Dim m As Match = rfc2822.Match(dateTimeString)
If m.Success Then
Try
Dim dd As Integer = Int32.Parse(m.Groups(1).Value)
Dim mth As Integer = months.IndexOf(m.Groups(2).Value)
Dim yy As Integer = Int32.Parse(m.Groups(3).Value)
' following year completion is compliant with RFC 2822.
'yy = (yy < 50 ? 2000 + yy: (yy < 1000 ? 1900 + yy: yy))
Dim hh As Integer = Int32.Parse(m.Groups(4).Value)
Dim mm As Integer = Int32.Parse(m.Groups(5).Value)
Dim ss As Integer = Int32.Parse(m.Groups(6).Value)
Dim zone As String = m.Groups(7).Value
Dim xd As New DateTime(yy, mth, dd, hh, mm, ss)
Return xd.AddHours(RFCTimeZoneToGMTBias(zone) * -1)
Catch ex As Exception
Throw New
FormatException("RES_ExceptionRFC2822ParseGroupsMessage")
End Try
Else
' fallback, if regex does not match:
Return DateTime.Parse(dateTimeString)
End If
End Function
Private Sub New()
'constructor is new to prevent creation, we just need the
statics
End Sub
Private Structure TZB
Public Sub New(ByVal z As String, ByVal b As Integer)
Zone = z
Bias = b
End Sub
Public Zone As String
Public Bias As Integer
End Structure
Private Const timeZones As Integer = 34
Private Shared ZoneBias As TZB() = New TZB(timeZones) { _
New TZB("GMT", 0), New TZB("UT", 0), _
New TZB("EST", -5 * 60), New TZB("EDT", -4 * 60), _
New TZB("CST", -6 * 60), New TZB("CDT", -5 * 60), _
New TZB("MST", -7 * 60), New TZB("MDT", -6 * 60), _
New TZB("PST", -8 * 60), New TZB("PDT", -7 * 60), _
New TZB("Z", 0), New TZB("A", -1 * 60), _
New TZB("B", -2 * 60), New TZB("C", -3 * 60), _
New TZB("D", -4 * 60), New TZB("E", -5 * 60), _
New TZB("F", -6 * 60), New TZB("G", -7 * 60), _
New TZB("H", -8 * 60), New TZB("I", -9 * 60), _
New TZB("K", -10 * 60), New TZB("L", -11 * 60), _
New TZB("M", -12 * 60), New TZB("N", 1 * 60), _
New TZB("O", 2 * 60), New TZB("P", 3 * 60), _
New TZB("Q", 4 * 60), New TZB("R", 3 * 60), _
New TZB("S", 6 * 60), New TZB("T", 3 * 60), _
New TZB("U", 8 * 60), New TZB("V", 3 * 60), _
New TZB("W", 10 * 60), New TZB("X", 3 * 60), _
New TZB("Y", 12 * 60)}
Private Shared Function RFCTimeZoneToGMTBias(ByVal zone As String)
As Double
Dim s As String
If zone.IndexOfAny(New Char() {"+"c, "-"c}) = 0 Then ' +hhmm
format
Dim fact As Integer
If zone.Substring(0, 1) = "-" Then
fact = -1
Else
fact = 1
End If
s = zone.Substring(1).TrimEnd()
Dim hh As Double = Math.Min(23, Int32.Parse(s.Substring(0,
2)))
Dim mm As Double = Math.Min(59, Int32.Parse(s.Substring(2,
2))) / 60
Return fact * (hh + mm)
Else
' named format
s = zone.ToUpper().Trim()
For i As Integer = 0 To timeZones
If (ZoneBias(i).Zone.Equals(s)) Then
Return ZoneBias(i).Bias / 60
End If
Next
End If
Return 0.0
End Function
Private Shared Function AddOffset(ByVal offsetOp As String, ByVal
datetimeString As String, ByVal tzoneIndex As Integer) As DateTime
Dim offset As String() = datetimeString.Substring(tzoneIndex +
1).Split(New Char() {":"c})
Dim original As String = datetimeString
datetimeString = datetimeString.Substring(0, tzoneIndex)
If (datetimeString.IndexOf(":") =
datetimeString.LastIndexOf(":")) Then 'check if seconds part is missing
datetimeString = datetimeString + ":00"
End If
Dim toReturn As DateTime =
System.Xml.XmlConvert.ToDateTime(datetimeString,
"yyyy-MM-ddTHH:mm:sszzzzzz")
Try
Select Case offsetOp
Case "+"
toReturn = toReturn.Subtract(New
TimeSpan(Int32.Parse(offset(0)), Int32.Parse(offset(1)), 0))
Case "-"
toReturn = toReturn.Add(New
TimeSpan(Int32.Parse(offset(0)), Int32.Parse(offset(1)), 0))
End Select
Return toReturn '.ToLocalTime() 'we treat all dates in feeds
as if they are local time (later)
Catch iex As IndexOutOfRangeException
Throw New
FormatException("RES_ExceptionRFC2822InvalidTimezoneFormatMessage")
End Try
End Function
End Class
End Namespace
--
Sincerely,
S. Justin Gengo, MCP
Web Developer / Programmer
www.aboutfortunate.com
"Out of chaos comes order."
Nietzsche
