Working with utcDateTime, time conversion, daylight

static void VKUTCToLocalDateTime(Args _args)
{
    timeZone        timeZone            = timeZone::GMT_DUBLIN_EDINBURGH_LISBON_LONDON; // DateTimeUtil::getUserPreferredTimeZone();
    utcDateTime     standardDateTime    = 2019-01-07T07:42:59, // winter time, standard
                    daylightDateTime    = 2019-07-10T10:42:59, // summer time, DST, daylight saving time
                    localDateTime;
    container       infoContainer;
    utcdatetime     dayLightStartDate;
    utcdatetime     dayLightEndDate;
    TimeBias        standardBias;
    TimeBias        dayLightBias;
    TimeZoneId      timeZoneId;
    
    // Easy conversion to local time
    // from UTC to GMT/BST (GB/UK/London);
    localDateTime = DateTimeUtil::applyTimeZoneOffset(standardDateTime, timeZone);
    localDateTime = DateTimeUtil::applyTimeZoneOffset(daylightDateTime, timeZone);
    
    // Hard way conversion daylightDateTime to local time, but with more control
    // Get timezone information container
    infoContainer = DateTimeUtil::populateTimeZoneInfo(DateTimeUtil::year(daylightDateTime), timeZone);
    
    dayLightStartDate   =   conPeek(infoContainer, 1);
    dayLightEndDate     =   conPeek(infoContainer, 2);
    standardBias        =   conPeek(infoContainer, 3);
    dayLightBias        =   conPeek(infoContainer, 4); // cumulative
    
    // substract time bias
    // https://stackoverflow.com/questions/2779948/subroutine-to-apply-daylight-bias-to-display-time-in-local-dst
    localDateTime       = DateTimeUtil::addMinutes(daylightDateTime, -standardBias);
    if (daylightDateTime >= dayLightStartDate && daylightDateTime <= dayLightEndDate)
    {
        localDateTime   = DateTimeUtil::addMinutes(localDateTime, -dayLightBias);
    }

    // UTC date time
    standardDateTime = DateTimeUtil::utcNow();
    
    // system date time
    standardDateTime = DateTimeUtil::getSystemDateTime();
    
    // Change the timezone information
    standardDateTime    = DateTimeUtil::removeTimeZoneOffset(localDateTime, timeZone);
    localDateTime       = DateTimeUtil::applyTimeZoneOffset(standardDateTime, timeZone::GMTPLUS0200HELSINKI_KYIV_RIGA_VILNIUS);
    
    // Timezone
    timeZone    = DateTimeUtil::getUserPreferredTimeZone();
    timeZoneId  = DateTimeUtil::getTimeZoneId(timeZone);
    
    // \Classes\RetailTimeZoneInfoJob\updateTimezoneInfoTable
    // Standard table TimezoneInfo is populated with timezone information
}