void QTimeZone::CalculateOffset(const QDateTime &dateTime, QTimeSpan &offset, bool &bIsNegative) const
{
// DST started to be applied in 1916
static const QDateTime FIRST_DATETIME_WITH_DST(1916, 1, 1);
// Boost can only process dates prior to the year 10.000
static const QDateTime MAXIMUM_DATETIME_WITH_DST = QDateTime(10000, 1, 1) - QTimeSpan(1);
QE_ASSERT(dateTime != QDateTime::GetUndefinedDate(), "The input date is undefined");
QTimeSpan dstOffset(0);
offset = m_timeZoneOffset;
if(m_bHasDstOffset && dateTime >= FIRST_DATETIME_WITH_DST && dateTime < MAXIMUM_DATETIME_WITH_DST)
{
QDateTime startDateTime = m_dstInformation.GetStartInYear(dateTime.GetYear());
QDateTime endDateTime = m_dstInformation.GetEndInYear(dateTime.GetYear());
if(dateTime >= startDateTime && dateTime < endDateTime)
{
if(!m_bTzOffsetIsNegative && !m_dstInformation.IsOffsetNegative())
{
// Both offsets are positive, they are summed
offset += m_dstInformation.GetOffset();
bIsNegative = false;
}
else if(m_bTzOffsetIsNegative && m_dstInformation.IsOffsetNegative())
{
// Both are negative, they are summed
offset += m_dstInformation.GetOffset();
bIsNegative = true;
}
else if(m_timeZoneOffset >= m_dstInformation.GetOffset())
{
// Time zone offset is bigger or equals the DST offset, the result is the difference
offset -= m_dstInformation.GetOffset();
bIsNegative = m_bTzOffsetIsNegative;
}
else
{
// Time zone offset is smaller than the DST offset, the result is the difference
offset = m_dstInformation.GetOffset() - offset;
bIsNegative = m_dstInformation.IsOffsetNegative();
}
}
else
{
bIsNegative = m_bTzOffsetIsNegative;
}
}
else
{
bIsNegative = m_bTzOffsetIsNegative;
}
}
