Probably there were 2 trains earlier (as i have heard), DLI- KIR MAHANANDA EXP and KIR-NJP SIKKIM EXP.....both the services were combined to form the DLI- NJP SIKKIM MAHANANDA EXP which was later extended to APDJ........earlier it used to be a train of NR and the train used to leave APDJ early in the morning around 7am and reach DLI by 18.30 next day.......later zone transfer was done and hence the present tt of it came into being.....