diff --git a/library/src/calculate_price.cpp b/library/src/calculate_price.cpp
index e2cde89..69730ca 100644
--- a/library/src/calculate_price.cpp
+++ b/library/src/calculate_price.cpp
@@ -233,7 +233,7 @@ CalcState CALCULATE_LIBRARY_API compute_duration_for_parking_ticket(
         duration = calculator.GetDurationFromCost(tariff, PaymentOption::Option1,
                                                   cs.toLocal8Bit().constData(),
                                                   price, false, true).c_str();
-        QDateTime d = QDateTime::fromString(duration);
+        QDateTime d = QDateTime::fromString(duration, Qt::ISODate);
         if (!d.isValid()) {
             calcState.setDesc(QString("ticketEndTime=%1").arg(duration));
             return calcState.set(CalcState::State::WRONG_ISO_TIME_FORMAT);