zone-events: Fixed flush replan.

src/knot/zone/events.c

@@ -621,7 +621,7 @@ static void replan_flush(zone_t *zone, const zone_t *old_zone)
 	}
 
 	// Pick time to schedule: either reuse or schedule sooner than old event.
-	const time_t schedule_at = MIN(time(NULL) - zone->conf->dbsync_timeout, flush_time);
+	const time_t schedule_at = MIN(time(NULL) + zone->conf->dbsync_timeout, flush_time);
 	zone_events_schedule_at(zone, ZONE_EVENT_FLUSH, schedule_at);
 }