Time Zone Information API

I have two questions relating to the Time Zone Info API;

1. how do I get the "current" time zone setting, and

2. standard & daylight dates are relative dates .. relative to what?

Thank you in advance, Bob.

Code:

---

Private Const TIME_ZONE_ID_UNKNOWN As Long = 1
Private Const TIME_ZONE_ID_STANDARD As Long = 1
Private Const TIME_ZONE_ID_DAYLIGHT As Long = 2
Private Const TIME_ZONE_ID_INVALID As Long = &HFFFFFFFF

Private Type SYSTEMTIME
  wYear        As Integer
  wMonth        As Integer
  wDayOfWeek    As Integer
  wDay          As Integer
  wHour        As Integer
  wMinute      As Integer
  wSecond      As Integer
  wMilliseconds As Integer
End Type

Private Type TIME_ZONE_INFORMATION
  Bias As Long
  StandardName(0 To ((32 * 2) - 1)) As Byte
  StandardDate As SYSTEMTIME
  StandardBias As Long
  DaylightName(0 To ((32 * 2) - 1)) As Byte
  DaylightDate As SYSTEMTIME
  DaylightBias As Long
End Type

Private Declare Function GetTimeZoneInformation Lib "kernel32" _
    (lpTimeZoneInformation As TIME_ZONE_INFORMATION) As Long



Private Sub Command1_Click()
  Dim tmp
  tmp = Format$(Now, "hh:mm:ss AMPM")
  Text1.Text = tmp & " " & GetCurrentTimeZone()


End Sub


Private Function IsDaylightSavingTime() As Boolean

  Dim tzi As TIME_ZONE_INFORMATION

  IsDaylightSavingTime = GetTimeZoneInformation(tzi) = TIME_ZONE_ID_DAYLIGHT

End Function


Private Function GetCurrentTimeZone() As String

  Dim tzi As TIME_ZONE_INFORMATION
  Dim tmp As String
  Dim pos As Integer
  Select Case GetTimeZoneInformation(tzi)
      Case 0:  tmp = "Cannot determine current time zone"
      Case 1:  tmp = tzi.StandardName
      Case 2:  tmp = tzi.DaylightName
  End Select
  pos = InStr(tmp, Chr$(0))
  If pos Then
        tmp = Left$(tmp, pos - 1)
    Else
        tmp = item
    End If
 
  GetCurrentTimeZone = tmp
 
End Function

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Daylight and standard time zones are set relative to your longitude - how far West or East you are from GMT (Greenwich Mean Time). 15 degrees of longitude is one hour - so most time zones are about that wide. Some time zones are on a 7.5 degree boundary - Macao for instance.

Jim

From this code segment;

Select Case GetTimeZoneInformation(tzi)
Case 0: tmp = "Cannot determine current time zone"
Case 1: tmp = tzi.StandardName
Case 2: tmp = tzi.DaylightName
End Select

am I correct to assume that the API returns 0 if unsuccessful, 1 if standard time in use and 2 if daylight time in use? If so, this isn't in my documentation.

I believe it is correct, since it has worked for a long time...

:D

Thanks Jim, Bob.