如何将日期、时间和 UTC 偏移量转换为本地日期时间

Question

我需要从以下 XML 元素中获取本地时区日期时间：

<TransactionDate>20191202</TransactionDate>
<TransactionTime>234026</TransactionTime>
<TransactionTimezone>UTC-06:00:00</TransactionTimezone>

我的本地 UTC 偏移量是 -05:00:00。 将 TransactionDate 和 TransactionTime 放入 td 和 tt Date 变量后，我可以像这样构建一个 Datetime：

Dim ldDate As New Date(td.Year, td.Month, td.Day, tt.Hour, tt.Minute, tt.Second)

我可以从 TransactionTimeZone 解析出 '-06' 并确定我需要向 ldDate 添加 1 小时，但必须有更优雅的方法。 有任何想法吗？

Answer 1

我编写了一个小程序，它从原始 TimeZone 中的 DateTime 返回本地 TimeZone 中的 DateTime：

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

我用这个调用它：

Dim lLocalDateTime as Date        
If Not P_ConvertToLocalDatetime(aTransactionDatetime, 
                                aTransactionTimezone, 
                                aLocalDateTime) Then
    Throw New Exception("Unable to convert TransactionDatetime to local time")
End If

...其中aTransactionTimezone是 String 类型，其值类似于"UTC-6:00:00" 。

Answer 2

如果您有来自世界各地的交易，这可能会帮助您作为基础并努力改进。

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

用法（此示例显示交易由 Hawai 完成）：

 ‘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)

要获取所有时区信息，您可以使用它来获得一个想法。

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