Option Explicit
 
Private Declare Function GetTimeZoneInformation Lib "kernel32" _
        (lpTimeZoneInformation As TIME_ZONE_INFORMATION) As Long
 
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(1 To 64) As Byte
  StandardDate As SYSTEMTIME
  StandardBias As Long
  DaylightName(1 To 64) As Byte
  DaylightDate As SYSTEMTIME
  DaylightBias As Long
End Type
 
Const TIME_ZONE_ID_UNKNOWN = &H0
Const TIME_ZONE_ID_STANDARD = &H1
Const TIME_ZONE_ID_DAYLIGHT = &H2
 
Public Function isWinter() As Boolean
 
 Dim tzi As TIME_ZONE_INFORMATION
 
  If (GetTimeZoneInformation(tzi) = TIME_ZONE_ID_DAYLIGHT) Then
   isWinter = False
  Else
   isWinter = True
  End If
 
End Function