How to prepone or postpone jorney
The date of journey on Confirmed/RAC/Waitlisted tickets can be
preponed or postponed in the same/higher class or for a longer
distance on payment of nominal charges. This facility can be availed
only...
more... once, irrespective of whether the accommodation available is
reserved or RAC or wait-listed.
If you want to prepone the date of your journey, you should
surrender your ticket during working hours and up to six hours
before the scheduled departure of the train in which fresh
reservation is required. For postponement, the ticket must be
surrendered at least 24 hours before the scheduled departure of
the train in which reservation is presently held.