You cant change the date of the ticket-you have to cancel it and book a fresh one-cancellation charges depdns on class of travel up Rs. Rs. 70/- for A.C First Class/Executive Class, Rs. 60/- for A.C. 2 Tier sleeper class/ A.C. 3 Tier sleeper class/ First class/A.C Chair Car, Rs. 40/- for Sleeper class and Rs. 20/- for Second class if ticket cancelled before 24 hrs of scheduled departure of the train- between 24 hrs and 4 hrscancellation charges will be 25% flat subject to above cancellation charges-and between 4 hrs and prescribed max limits it will be 50%