qcandlestickset does not support negative timestamp

qcandlestickset does not support negative timestamp.  It automatically sets the timestamp to 0 if a negative number is used.  Negative number is a valid timestamp.   QDateTime supports negative epoch timestamp.  For example, the following code will print "1969/09/18".

QDateTime::fromMSecsSinceEpoch(-9000000000).toString("yyyy/MM/dd")