Arrival time of Kalka Shatabdi at Kalka in Dec is 12.20 pm (1st Dec), 11.54 am (2nd Dec) and 11.54 (ETA on 3rd Dec). So you must be an ETERNAL OPTIMIST to bank on this connection unless there is an informal arrangement at Kalka whereby 255 Kalka Shimla Exp waits for Kalka Shatabdi to arrive.