Public Function DateAddTimeZoneDiff( _
  ByVal datLocal As Date, _
  ByVal lngLocalBias, _
  ByVal lngRemoteBias) _
  As Date
  
' Calculates the date/time of datLocal in a remote time zone.
' Adds the difference in minutes between the local time zone bias and
' the remote time zone bias, if both bias are relative to UTC.
'
' Examples:
'
'   datRemote = DateAddTimeZoneDiff(Now(), 60, -600)
' will return datRemote as eleven hours ahead of local time.
'
'   datRemote = DateAddTimeZoneDiff(Now(), -600, 60)
' will return datRemote as eleven hours behind local time.
'
' 2000-05-30. Cactus Data ApS, CPH.
' 2005-01-25. Adjusted to accommodate change in TimeZoneBiasDiff().
 
  Dim datRemote As Date
  Dim lngBias   As Long
  
  ' Get difference (in minutes) in time zone bias.
  lngBias = TimeZoneBiasDiff(lngLocalBias, lngRemoteBias)
  ' Calculate remote date/time.
  datRemote = DateAdd("n", lngBias, datLocal)
  
  DateAddTimeZoneDiff = datRemote
  
End Function
 
 
Public Function TimeZoneBiasDiff( _
  ByVal lngLocalTimeBias As Long, _
  ByVal lngRemoteTimeBias As Long) _
  As Long
  
' Calculates the difference in minutes between two time zones,
' typically from the local time zone to the remote time zone.
' Both time zones must be expressed by their bias relative to
' UTC (Coordinated Universal Time) which is measured in minutes.
'
' 2000-05-30. Cactus Data ApS, CPH.
' 2005-01-25. Output reversed to express bias value.
 
  ' Minimum amount of minutes for a time zone bias.
  Const clngTimeZoneBiasMin As Long = 15
 
  Dim lngTimeZoneBiasDiff As Long
  
  ' Round off time zone bias by minimum time zone difference.
  lngLocalTimeBias = lngLocalTimeBias \ clngTimeZoneBiasMin
  lngLocalTimeBias = lngLocalTimeBias * clngTimeZoneBiasMin
  lngRemoteTimeBias = lngRemoteTimeBias \ clngTimeZoneBiasMin
  lngRemoteTimeBias = lngRemoteTimeBias * clngTimeZoneBiasMin
  
  ' Calculate difference in time zone bias.
  lngTimeZoneBiasDiff = lngLocalTimeBias - lngRemoteTimeBias
  
  TimeZoneBiasDiff = lngTimeZoneBiasDiff
 
End Function