diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index 9442587..65b7a9c 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -118,17 +118,21 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
                                             bool nextDay,
                                             bool prepaid)
 {
+
+    // Get input date
+    QDateTime inputDate = QDateTime::fromString(start_datetime,Qt::ISODate);
+
     // use tariff with structure as for instance Schnau, Koenigsee:
     // without given YearPeriod, SpecialDays and SpecialDaysWorktime
     if (cfg->YearPeriod.size() == 0
         && cfg->SpecialDays.size() == 0
         && cfg->SpecialDaysWorktime.size() == 0)
     {
-        return QString().setNum(GetDurationForPrice(cfg, price)).toStdString();
+        inputDate = inputDate.addSecs(GetDurationForPrice(cfg, price) * 60);
+
+        return inputDate.toString(Qt::ISODate).toStdString();
     }
 
-    // Get input date
-    QDateTime inputDate = QDateTime::fromString(start_datetime,Qt::ISODate);
 
     // Get day of week
     int weekdayId = 0;
@@ -633,14 +637,16 @@ uint32_t Calculator::GetPriceForTimeStep(Configuration *cfg, int timeStep) const
 uint32_t Calculator::GetDurationForPrice(Configuration *cfg, int price) const {
     int const pop_id = cfg->getPaymentOptions().pop_id;
 
+
     for (auto[itr, rangeEnd] = cfg->PaymentRate.equal_range(pop_id); itr != rangeEnd; ++itr)
     {
         int const payment_unit_id = itr->second.pra_payment_unit_id;
-        int const pra_price = cfg->PaymentRate.find(payment_unit_id)->second.pra_price;
+        int const pra_price = itr->second.pra_price;
 
         if (price == pra_price) {
             int const durationId = itr->second.pra_payment_unit_id;
             int const durationUnit = cfg->Duration.find(durationId)->second.pun_duration;
+
             return durationUnit;
         }
     }