GetTimeZoneInformation Issue

[westconn1]

in an application i have been using buggy code for 4 years, without realising till this thread, mostly the time difference was correct, if it was out of sync for a week at the time of daylight saving change, i never noticed

still it is better to have the code working correctly

[Hassan Basri]

in an application i have been using buggy code for 4 years, without realising till this thread, mostly the time difference was correct, if it was out of sync for a week at the time of daylight saving change, i never noticed

still it is better to have the code working correctly

Hello westconn, I was in the exact same situation. I had some users complain and that was how I found out. You are correct certain daylight savings time change dates were 1 week off. I have an option in the application for a manual adjustment which is what I told the users to do during that one week.

I tried your code but got incorrect results. I recreated the function format from vbnet but inserted your code. This is what it looks like:

Private Function GetTimezoneChangeDate(tziDate As SYSTEMTIME, _
                                       ByVal tziYear As Long, _
                                       ByVal dwType As DateFormats) As String

  'thanks to Mathias Schiffer for this routine
  
   Dim tmp As Date
   Dim MonthFirstWeekday As Long
   Dim fday As Integer
   Dim j As Integer

   With tziDate

      Dim iFirstDay As Integer
      Dim iDay As Integer
      Dim lday As Integer

        fday = Weekday(DateSerial(tziYear, .wMonth, 1))
        j = (.wDayOfWeek - 1) * 7 + (2 - fday) + iDay
        If j < 1 Then j = j + 7  ' fixed here
        tmp = DateSerial(tziYear, .wMonth, j)
          '*********** fred zone code
              iFirstDay = Weekday(DateSerial(tziYear, .wMonth, 1))
              lday = iDay + 1
              If iFirstDay > 0 Then lday = 9 - iFirstDay
              lday = lday + (7 * (iDay - 1))
              GetTimezoneChangeDate = DateSerial(tziYear, .wMonth, iDay)
             ' *************

   End With
   
  'Now that the date has been calculated,
  'return it in the string format requested
  'In VB6, you can use the FormatDateTime
  'function to return date in specified format
   GetTimezoneChangeDate = Format$(tmp, "MMMM dd")
   
End Function