diff --git a/src/calculation_time_constrains/service.py b/src/calculation_time_constrains/service.py
index 12f9b11..667d10f 100644
--- a/src/calculation_time_constrains/service.py
+++ b/src/calculation_time_constrains/service.py
@@ -1240,7 +1240,7 @@ class OptimumCostModel:
             total_costs = total_corrective_costs + total_preventive_costs + total_procurement_costs
             fleet_optimal_index = np.argmin(total_costs)
 
-            calculation.optimum_oh_day = fleet_optimal_index + 1
+            calculation.optimum_oh_day = fleet_optimal_index
             calculation.max_interval = max_interval-1