The QDateConvertor class can help you convert the geogeodate form to jalali and jalali to geogorian.
Edit:
Add this class to your project and include "qdateconvertor.h" where you need to convert the date.
QDateConvertor mdate;
QStringList shamsi= mdate.ToJalali( "2001","9","11");
QString JalailDate =shamsi.at(0)+"/"+shamsi.at(1)+"/"+shamsi.at(2)+ ":" +shamsi.at(3);
qDebug()<<JalailDate;
QStringList m= mdate.ToMiladi("1372","3","6");
QString miladiDate= m.at(0)+"/"+ m.at(1)+"/"+m.at(2);
qDebug()<<miladiDate;
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