diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index 5309bbc..0b085c4 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -615,8 +615,259 @@ uint32_t Calculator::GetCostFromDuration(Configuration * cfg,
     return 0;
 }
 
+CalcState Calculator::isParkingAllowedForWeekDay(Configuration const *cfg,
+                                                 QDateTime const &start,
+                                                 int netto_parking_time,
+                                                 int paymentOptionIndex) {
 
-CalcState Calculator::isParkingAllowed(Configuration const *cfg, QDateTime const &start) {
+    qCritical() << DBG_HEADER << "start" << start.toString(Qt::ISODate)
+                << "paymentOptionIndex" << paymentOptionIndex;
+
+    QString errorStr = "UNKNOWN ERROR";
+
+    PaymentMethod const paymentMethodId = Utilities::getPaymentMethodId(cfg);
+    if (paymentMethodId == PaymentMethod::Steps) {
+        uint64_t const businessHours = cfg->getPaymentOptions(paymentOptionIndex).pop_business_hours;
+        if (cfg->isDayIncluded(businessHours, start)) {
+            if (businessHours == BusinessHours::NO_RESTRICTION_24_7) {
+                return CalcState(CalcState::State::SUCCESS, "PARKING_ALLOWED",
+                         QTime(0, 0, 0), QTime(23, 59, 59));
+            }
+            int const weekdayId = start.date().dayOfWeek();
+            if (cfg->WeekDaysWorktime.count(weekdayId) > 0) {
+                using WTIterator = std::multimap<int, ATBWeekDaysWorktime>::const_iterator;
+                std::pair<WTIterator, WTIterator> p = cfg->WeekDaysWorktime.equal_range(weekdayId);
+
+                for (WTIterator itr = p.first; itr != p.second; ++itr) {
+                    QTime const &from = Utilities::WeekDaysWorkTimeFrom(itr);
+                    QTime const &until = Utilities::WeekDaysWorkTimeUntil(itr);
+
+                    qCritical() << DBG_HEADER
+                                << "CHECK IF PARKING IS ALLOWED IN TIME-RANGE ("
+                                << from.toString(Qt::ISODate) << "->" << until.toString(Qt::ISODate) << ") ...";
+
+                    QTime const &startTime = start.time();
+
+                    if (startTime >= from && startTime <= until) {
+                        QTime const endTime = start.addSecs(netto_parking_time*60).time();
+                        if (endTime <= until) {
+                            return CalcState(CalcState::State::SUCCESS, "PARKING_ALLOWED", from, until);
+                        } else {
+                            errorStr = QString("%1 startTime not in range (%2 not in [%3, %4))")
+                                                .arg(__LINE__)
+                                                .arg(startTime.toString(Qt::ISODate))
+                                                .arg(from.toString(Qt::ISODate))
+                                                .arg(endTime.toString(Qt::ISODate));
+                        }
+                    } else {
+                        errorStr = QString("%1 startTime not in range (%2 not in [%3, %4))")
+                                            .arg(__LINE__)
+                                            .arg(startTime.toString(Qt::ISODate))
+                                            .arg(from.toString(Qt::ISODate))
+                                            .arg(until.toString(Qt::ISODate));
+                    }
+
+                    int const pop_carry_over = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over;
+                    if (pop_carry_over == 1) {
+                        qCritical() << DBG_HEADER
+                                    << "NO. CHECK IF PARKING IS ALLOWED WITH CARRY-OVER ...";
+
+                        int const pop_carry_over_start_time_range = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over_start_time_range;
+                        int const pop_carry_over_end_time_range = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over_end_time_range;
+
+                        if (cfg->TimeRange.count(pop_carry_over_start_time_range) == 1 &&
+                            cfg->TimeRange.count(pop_carry_over_end_time_range) == 1) {
+
+                            ATBTimeRange s = cfg->TimeRange.find(pop_carry_over_start_time_range)->second;
+                            ATBTimeRange e = cfg->TimeRange.find(pop_carry_over_end_time_range)->second;
+
+                            if (startTime >= s.getTimeFrom() && startTime <= s.getTimeUntil()) {
+                                QDateTime sd = start;
+                                sd.setTime(s.getTimeUntil());
+
+                                QDateTime ed = start.addDays(1);
+                                ed.setTime(e.getTimeFrom());
+
+                                int const jumpSecs = sd.secsTo(ed);
+                                QDateTime const end = start.addSecs(netto_parking_time*60 + jumpSecs);
+                                if (end.time() <= e.getTimeUntil()) {
+
+                                    qCritical() << DBG_HEADER
+                                                << "PARKING IS ALLOWED WITH CARRY-OVER ("
+                                                << start.toString(Qt::ISODate) << "->" << ed.toString(Qt::ISODate) << ")";
+
+                                    return CalcState(CalcState::State::SUCCESS, "PARKING_ALLOWED",
+                                                     startTime, end.time());
+                                } else {
+                                    errorStr = QString("endTime %1 exceeds [%2, %3))")
+                                                  .arg(end.toString(Qt::ISODate))
+                                                  .arg(sd.toString(Qt::ISODate))
+                                                  .arg(ed.toString(Qt::ISODate));
+                                }
+                            } else {
+                                errorStr = QString("startTime %1 exceeds [%2, %3))")
+                                              .arg(startTime.toString(Qt::ISODate))
+                                              .arg(s.getTimeFrom().toString(Qt::ISODate))
+                                              .arg(s.getTimeUntil().toString(Qt::ISODate));
+                            }
+                        } else {
+                           errorStr = "no carry-over limits configured";
+                        }
+                    } else {
+                        errorStr = "no carry-over configured";
+                    }
+                }
+            } else {
+                errorStr = QString("no weekday configured for day-id %1").arg(weekdayId);
+            }
+
+        } else {
+            errorStr = QString("start %1 not contained in business hours %2")
+                            .arg(start.toString(Qt::ISODate))
+                            .arg(businessHours);
+        }
+    }
+
+    return CalcState(CalcState::State::OUTSIDE_ALLOWED_PARKING_TIME, errorStr,
+                     QTime(), QTime());
+}
+
+
+CalcState Calculator::isParkingAllowedForSpecialDay(Configuration const *cfg,
+                                                    QDateTime const &start,
+                                                    int netto_parking_time,
+                                                    int paymentOptionIndex) {
+    QString errorStr = "UNKNOWN ERROR";
+
+    qCritical() << DBG_HEADER << "start" << start.toString(Qt::ISODate)
+                << "paymentOptionIndex" << paymentOptionIndex;
+
+    PaymentMethod const paymentMethodId = Utilities::getPaymentMethodId(cfg);
+    if (paymentMethodId == PaymentMethod::Steps) {
+        //uint64_t const businessHours = cfg->getPaymentOptions(paymentOptionIndex).pop_business_hours;
+        int const specialDayId = cfg->specialDayId(start);
+        if ((specialDayId > 0) && (cfg->SpecialDaysWorktime.count(specialDayId) > 0)) {
+            using SDIterator = Configuration::SpecialDaysWorktimeType::const_iterator;
+            std::pair<SDIterator, SDIterator> p = cfg->SpecialDaysWorktime.equal_range(specialDayId);
+
+            for (SDIterator it = p.first; it != p.second; ++it) {
+                QTime const &from = Utilities::SpecialDaysWorkTimeFrom(it);
+                QTime const &until = Utilities::SpecialDaysWorkTimeUntil(it);
+
+                qCritical() << DBG_HEADER
+                            << "CHECK IF PARKING IS ALLOWED IN TIME-RANGE ("
+                            << from.toString(Qt::ISODate) << "->" << until.toString(Qt::ISODate) << ") ...";
+
+                QTime const &startTime = start.time();
+
+                if (startTime >= from && startTime <= until) {
+                    QTime const endTime = start.addSecs(netto_parking_time*60).time();
+                    if (endTime <= until) {
+                        return CalcState(CalcState::State::SUCCESS, "PARKING_ALLOWED", from, until);
+                    } else {
+                        errorStr = QString("%1 startTime not in range (%2 not in [%3, %4))")
+                                            .arg(__LINE__)
+                                            .arg(startTime.toString(Qt::ISODate))
+                                            .arg(from.toString(Qt::ISODate))
+                                            .arg(endTime.toString(Qt::ISODate));
+                    }
+                } else {
+                    errorStr = QString("%1 startTime not in range (%2 not in [%3, %4))")
+                                        .arg(__LINE__)
+                                        .arg(startTime.toString(Qt::ISODate))
+                                        .arg(from.toString(Qt::ISODate))
+                                        .arg(until.toString(Qt::ISODate));
+                }
+
+                int const pop_carry_over = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over;
+                if (pop_carry_over == 1) {
+                    qCritical() << DBG_HEADER << "NO. CHECK IF PARKING IS ALLOWED WITH CARRY-OVER ...";
+
+                    int const pop_carry_over_start_time_range = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over_start_time_range;
+                    int const pop_carry_over_end_time_range = cfg->getPaymentOptions(paymentOptionIndex).pop_carry_over_end_time_range;
+
+                    if (cfg->TimeRange.count(pop_carry_over_start_time_range) == 1 &&
+                        cfg->TimeRange.count(pop_carry_over_end_time_range) == 1) {
+
+                        ATBTimeRange s = cfg->TimeRange.find(pop_carry_over_start_time_range)->second;
+                        ATBTimeRange e = cfg->TimeRange.find(pop_carry_over_end_time_range)->second;
+
+                        if (startTime >= s.getTimeFrom() && startTime <= s.getTimeUntil()) {
+                            QDateTime sd = start;
+                            sd.setTime(s.getTimeUntil());
+
+                            QDateTime ed = start.addDays(1);
+                            ed.setTime(e.getTimeFrom());
+
+                            int const jumpSecs = sd.secsTo(ed);
+                            QDateTime const end = start.addSecs(netto_parking_time*60 + jumpSecs);
+                            if (end.time() <= e.getTimeUntil()) {
+
+                                ed.setTime(e.getTimeUntil()); // for printing
+
+                                qCritical() << DBG_HEADER
+                                            << "PARKING IS ALLOWED WITH CARRY-OVER ("
+                                            << start.toString(Qt::ISODate) << "->" << ed.toString(Qt::ISODate) << ")";
+
+                                return CalcState(CalcState::State::SUCCESS, "PARKING_ALLOWED",
+                                                 startTime, end.time());
+                            } else {
+                                ed.setTime(e.getTimeUntil()); // for printing
+
+                                errorStr = QString("endTime %1 exceeds [%2, %3))")
+                                              .arg(end.toString(Qt::ISODate))
+                                              .arg(sd.toString(Qt::ISODate))
+                                              .arg(ed.toString(Qt::ISODate));
+                            }
+                        } else {
+                            errorStr = QString("startTime %1 exceeds [%2, %3))")
+                                          .arg(startTime.toString(Qt::ISODate))
+                                          .arg(s.getTimeFrom().toString(Qt::ISODate))
+                                          .arg(s.getTimeUntil().toString(Qt::ISODate));
+                        }
+                    } else {
+                       errorStr = "no carry-over limits configured";
+                    }
+                } else {
+                    errorStr = "no carry-over configured";
+                }
+            }
+        }
+    }
+
+    return CalcState(CalcState::State::OUTSIDE_ALLOWED_PARKING_TIME, errorStr,
+                     QTime(), QTime());
+}
+
+
+CalcState Calculator::isParkingAllowed(Configuration const *cfg,
+                                       QDateTime const &start,
+                                       int netto_parking_time,
+                                       int paymentOptionIndex) {
+
+    qCritical() << DBG_HEADER << "CHECK IF PARKING IS ALLOWED AT"
+                << start.toString(Qt::ISODate) << "...";
+
+    CalcState cs;
+
+    if ((cs = isParkingAllowedForWeekDay(cfg, start, netto_parking_time, paymentOptionIndex))) {
+        return cs;
+    }
+
+    qCritical() << DBG_HEADER << QString(cs);
+
+    if ((cs = isParkingAllowedForSpecialDay(cfg, start, netto_parking_time, paymentOptionIndex))) {
+        return cs;
+    }
+
+    qCritical() << DBG_HEADER << QString(cs);
+
+    return CalcState(CalcState::State::OUTSIDE_ALLOWED_PARKING_TIME, "UNKNOWN ERROR",
+                     QTime(), QTime());
+}
+
+CalcState Calculator::isParkingAllowed(Configuration const *cfg,
+                                       QDateTime const &start) {
     static const PaymentMethod paymentMethodId = Utilities::getPaymentMethodId(cfg);
 
     if (paymentMethodId == PaymentMethod::Steps) {