How to Convert Date, Time and UTC Offset to Local DateTime - vb.net

Question

I need to get a local timezone datetime from the following XML elements:
<TransactionDate>20191202</TransactionDate>
<TransactionTime>234026</TransactionTime>
<TransactionTimezone>UTC-06:00:00</TransactionTimezone>
My local UTC offset is -05:00:00. After getting TransactionDate and TransactionTime into td and tt Date variables, I can build a Datetime like this:
Dim ldDate As New Date(td.Year, td.Month, td.Day, tt.Hour, tt.Minute, tt.Second)
I could parse out the '-06' from TransactionTimeZone and determine that I need to add 1 hour to ldDate, but there must be a more elegant way. Any ideas?

Answer 1

I wrote a small procedure that returns a DateTime in the local TimeZone from a DateTime in an originating TimeZone:
Public Function P_ConvertToLocalDatetime(ByVal aOriginDateTime As Date,
ByVal aOriginTimeZone As String,
ByRef aLocalDateTime As Date) As Boolean
Try
Dim liHour As Integer = CInt(Strings.Mid(aOriginTimeZone, 4, 3))
Dim liMinute As Integer = CInt(Strings.Mid(aOriginTimeZone, 8, 2))
Dim liSecond As Integer = CInt(Strings.Right(aOriginTimeZone, 2))
With aOriginDateTime
Dim offset As New DateTimeOffset(.Year, .Month, .Day, .Hour, .Minute, .Second, New TimeSpan(liHour, liMinute, liSecond))
aLocalDateTime = offset.LocalDateTime
End With
Return True
Catch ex As Exception
Return False
End Try
End Function
I'm calling it with this:
Dim lLocalDateTime as Date
If Not P_ConvertToLocalDatetime(aTransactionDatetime,
aTransactionTimezone,
aLocalDateTime) Then
Throw New Exception("Unable to convert TransactionDatetime to local time")
End If
... where aTransactionTimezone is of type String with a value like "UTC-6:00:00".

Answer 2

If you have transactions from all the world this might help you to use as a base and working on to improve.
Private Function FromWorldTimeToMyLocalTime(noSpacesDateTimeTransaction As String, transactionZoneString As String) As Date
Dim transactionDtTime As Date = Date.ParseExact(noSpacesDateTimeTransaction, "yyyyMMddHHmmss", Globalization.CultureInfo.InvariantCulture)
Return DateAndTime.DateAdd(DateInterval.Hour, TimeZoneInfo.FindSystemTimeZoneById(transactionZoneString).BaseUtcOffset.TotalHours, transactionDtTime)
End Function
Usage (Here the example shows a transaction is done by Hawai):
‘Here is your complete string as you have in your xml tags (date + time) it’s presumed the transaction is come by Hawai
Dim myDateTimeFromTransactionTime As String = FromWorldTimeToMyLocalTime("20191202234026", "Hawaiian Standard Time").ToString
Console.WriteLine("MyTime from transaction is " & myDateTimeFromTransactionTime)
To get all timezone infos you can use this to have an idea.
Dim timeZones As ReadOnlyCollection(Of TimeZoneInfo) = TimeZoneInfo.GetSystemTimeZones()
For Each timeZoneInfo As TimeZoneInfo In timeZones
Console.WriteLine(CStr(timeZoneInfo.Id) & " " & CStr(timeZoneInfo.BaseUtcOffset.TotalHours))
Next