diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index a3233bc..a97c02d 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -225,7 +225,7 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
 
     if (calc_price > 0 && total_duration_min > 0)
     {
-        inputDate.addSecs(-(int)ceil(calc_price) * 60);
+        inputDate = inputDate.addSecs(-(int)ceil(calc_price) * 60);
     }
 
     if(price >= min_price && total_duration_min >= minMin)