Working with Time Zones

In addition to providing access to the various Outlook folder objects, the IPOutlookApp interface has two support functions that are used for handling time zone information. The first function, IPOutlookApp::GetTimeZoneInformationFromIndex(), uses the standard Windows CE TIME_ZONE_INFORMATION structure to retrieve time zone information. The function is defined as follows:

 HRESULT IPOutlookApp::GetTimeZoneInformationFromIndex(int   cTimezone, TIME_ZONE_INFORMATION *ptzInfo); 

The Pocket Outlook Object Model also provides the ITimeZone interface, which is used for retrieving information about daylight savings time for a particular time zone. To get a pointer to the ITimeZone object, you can use the following function:

 HRESULT IPOutlookApp::GetTimeZoneFromIndex(int cTimezone,    ITimeZone **ppTz); 

The first parameter is the index to the time zone that you are interested in, and is followed by a pointer to a pointer value that will be filled in with the ITimeZone interface.

Table 10.3 describes the properties supported by the ITimeZone interface.

Table 10.3. ITimeZone pPoperties

Property	Get/Put	Description
Application	Get	Returns a pointer to the IPOutlookApp interface.
Bias	Get	Gets the current bias, in minutes, for the local time translations (UTC = Local Time + Bias).
DaylightBias	Get	Gets the offset, in minutes, when a time zone is in daylight savings time.
DaylightDate	Get	Gets the date when the time returns to daylight savings time.
DaylightDayOfWeekMask	Get	Gets the day of the week on which daylight savings time begins.
DaylightInstance	Get	Gets the week of the month in which daylight savings time begins.
DaylightMonthOfYear	Get	Gets the month of the year in which daylight savings time begins.
DaylightName	Get	Gets the name of the time zone when in daylight savings time.
IsDaylightAbsoluteDate	Get	Indicates whether the daylight date is the absolute or relative date. Returns TRUE if it is the standard date, FALSE if it is relative.
IsStandardAbsoluteDate	Get	Indicates whether the standard date is the absolute or relative date. Returns TRUE if it is the standard date, FALSE if it is relative.
StandardBias	Get	Gets the offset, in minutes, when a time zone is in standard time.
StandardDate	Get	Indicates when the date returns to a standard time.
StandardDayOfWeekMask	Get	Gets the day of the week on which standard time returns from daylight savings time.
StandardInstance	Get	Gets the week of the month (from 1 to 5) in which standard time begins.
StandardMonthOfYear	Get	Gets the month of the year in which standard time begins.
StandardName	Get	Gets the name of the time zone when in standard time.
SupportsDST	Get	Indicates whether the time zone supports daylight savings time.

The following short code example shows how you can get time zone information for Pacific Standard Time:

 // Get the time zone information for PST ITimeZone *pTimeZone = NULL; hr = pOlApp->GetTimeZoneFromIndex(4, &pTimeZone); if(FAILED(hr))    OutputDebugString(TEXT("Could not get the calendar       folder")); else {    TCHAR tchDaylightStart[256] = TEXT("\0");    TCHAR tchStandardStart[256] = TEXT("\0");    // Figure out daylight savings time    BSTR bstrName = NULL;    SYSTEMTIME stDaylight;    VARIANT_BOOL vbDate;    hr = pTimeZone->get_DaylightName(&bstrName);    if(FAILED(hr))       return FALSE;    // PST uses a relative date, but let's just make sure    pTimeZone->get_IsDaylightAbsoluteDate(&vbDate);    if(vbDate == VARIANT_FALSE) {       DATE pDaylight = NULL;       LONG lDayOfWeek = 0, lMonth = 0, lDayInstance = 0;       // Get the date       if(FAILED(pTimeZone->get_DaylightDayOfWeekMask              (&lDayOfWeek)))          return FALSE;       if(FAILED(pTimeZone->get_DaylightInstance              (&lDayInstance)))          return FALSE;       if(FAILED(pTimeZone->get_DaylightMonthOfYear(&lMonth)))          return FALSE;       // Get the time       if(FAILED(pTimeZone->get_DaylightDate(&pDaylight)))          return FALSE;       // Fill out the structure:       memset(&stDaylight, 0, sizeof(SYSTEMTIME));       VariantTimeToSystemTime(pDaylight, &stDaylight);       wsprintf(tchDaylightStart,          TEXT("%s\r\nDaylight Savings Time will          begin:\r\nWeek: %d\r\nDay of          Week: %d\r\nMonth: %d\r\nat %d:%d"), bstrName,          lDayOfWeek, lDayInstance, lMonth, stDaylight.wHour,          stDaylight.wMinute);     } else {        // Place absolute date handler stuff here     }    // MessageBox    MessageBox(NULL, tchDaylightStart, TEXT("Daylight"),         MB_OK);    // Free resources    SysFreeString(bstrName); } if(pTimeZone)    pTimeZone->Release();