Approval in backend

backend/kn/calendar.json

@@ -0,0 +1,9 @@
+{
+    "calendar": {
+        "all_calendars": "All calendars",
+        "exhibition_starts": "Exhibition starts",
+        "exhibition_ends": "Exhibition ends",
+        "loan_starts": "Loan starts",
+        "loan_ends": "Loan ends"
+    }
+}