It is an unique train of Indian Railways. As it has the same tt which is updated here or in NTES. But it regularly gets rescheduled on every Tuesday, Thursday and Saturday (one can track). Actually there are no technical or any reason but it follows a different time schedule specially on that days like 18:00 dep Ranchi and 00:00 arr GBA. Can be called as un Official TT. Any RNC or GBS based members can confirm.
Note: Only one sided that is from Ranchi