diff --git a/src/order_cmd.cpp b/src/order_cmd.cpp
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@@ -1947,10 +1947,10 @@ VehicleOrderID ProcessConditionalOrder(c
 		case OCV_RELIABILITY:        skip_order = OrderConditionCompare(occ, ToPercent16(v->reliability),       value); break;
 		case OCV_MAX_RELIABILITY:    skip_order = OrderConditionCompare(occ, ToPercent16(v->GetEngine()->reliability),   value); break;
 		case OCV_MAX_SPEED:          skip_order = OrderConditionCompare(occ, v->GetDisplayMaxSpeed() * 10 / 16, value); break;
-		case OCV_AGE:                skip_order = OrderConditionCompare(occ, DateToYear(v->age),                value); break;
+		case OCV_AGE:                skip_order = OrderConditionCompare(occ, TimerGameCalendar::DateToYear(v->age),                value); break;
 		case OCV_REQUIRES_SERVICE:   skip_order = OrderConditionCompare(occ, v->NeedsServicing(),               value); break;
 		case OCV_UNCONDITIONALLY:    skip_order = true; break;
-		case OCV_REMAINING_LIFETIME: skip_order = OrderConditionCompare(occ, std::max(DateToYear(v->max_age - v->age + DAYS_IN_LEAP_YEAR - 1), TimerGameCalendar::Year(0)), value); break;
+		case OCV_REMAINING_LIFETIME: skip_order = OrderConditionCompare(occ, std::max(TimerGameCalendar::DateToYear(v->max_age - v->age + CalendarTime::DAYS_IN_LEAP_YEAR - 1), TimerGameCalendar::Year(0)), value); break;
 		default: NOT_REACHED();
 	}