diff --git a/library/include/mobilisis/calculator_functions.h b/library/include/mobilisis/calculator_functions.h
index c156f8d..2f72ca6 100644
--- a/library/include/mobilisis/calculator_functions.h
+++ b/library/include/mobilisis/calculator_functions.h
@@ -14,7 +14,7 @@
 using namespace std;
 
 class Calculator {
-    mutable QList<int> m_timeSteps;
+    mutable QVector<QList<int>> m_timeSteps;
     mutable QList<int> m_priceSteps;
 
 protected:
@@ -29,8 +29,17 @@ public:
         return c;
     }
 
-    void ResetTimeSteps() { m_timeSteps.clear(); }
-    QList<int> timeSteps() const { return m_timeSteps; }
+    void ResetTimeSteps(int paymentOptionIndex) {
+        if (m_timeSteps.size() > 0) {
+            m_timeSteps[paymentOptionIndex].clear();
+        }
+    }
+    QList<int> timeSteps(int paymentOptionIndex=0) const {
+        if (m_timeSteps.size() > 0) {
+            return m_timeSteps[paymentOptionIndex];
+        }
+        return QList<int>();
+    }
 
     void ResetPriceSteps() { m_priceSteps.clear(); }
     QList<int> priceSteps() const { return m_priceSteps; }
@@ -66,8 +75,8 @@ public:
     // helper function to find time steps for a tariff with PaymentMethod::Steps
     // (e.g. Schoenau/Koenigsee)
     //
-    QList<int> GetTimeSteps(Configuration *cfg) const;
-    QList<int> GetSteps(Configuration *cfg) const { return GetTimeSteps(cfg); }
+    QList<int> GetTimeSteps(Configuration *cfg, int paymentOptionIndex=0) const;
+    QList<int> GetSteps(Configuration *cfg, int paymentOptionIndex=0) const { return GetTimeSteps(cfg, paymentOptionIndex); }
 
     QList<int> GetPriceSteps(Configuration *cfg) const;