diff --git a/grocy/config.json b/grocy/config.json
index dcfefee..6087637 100755
--- a/grocy/config.json
+++ b/grocy/config.json
@@ -63,6 +63,7 @@
       "tasks": "bool"
     },
     "tweaks": {
+      "calendar_first_day_of_week": "int(0,6)?",
       "chores_assignment": "bool",
       "meal_plan_first_day_of_week": "int(0,6)?",
       "multiple_shopping_lists": "bool",
diff --git a/grocy/rootfs/etc/services.d/php-fpm/run b/grocy/rootfs/etc/services.d/php-fpm/run
index 99f583c..d703fa5 100644
--- a/grocy/rootfs/etc/services.d/php-fpm/run
+++ b/grocy/rootfs/etc/services.d/php-fpm/run
@@ -3,6 +3,7 @@
 # Home Assistant Community Add-on: Grocy
 # Runs the PHP-FPM daemon
 # ==============================================================================
+declare caldayweek
 declare mealday
 export GROCY_CULTURE
 export GROCY_CURRENCY
@@ -42,6 +43,11 @@ if bashio::config.false 'features.tasks'; then
     export GROCY_FEATURE_FLAG_TASKS=0
 fi
 
+if bashio::config.has_value 'tweaks.calendar_first_day_of_week'; then
+    caldayweek=$(bashio::config 'tweaks.calendar_first_day_of_week')
+    export GROCY_CALENDAR_FIRST_DAY_OF_WEEK=${caldayweek}
+fi
+
 if bashio::config.false 'tweaks.chores_assignment'; then
     export GROCY_FEATURE_FLAG_CHORES_ASSIGNMENTS=0
 fi