Mar 14, 2016 - 04:48 AM
The ticket if it is a regional train ticket should advise you in the instructions that it it valid for 2 months from date
of purchase on that specific route at any time, so you may just print it when you are going to use it and valdiate
the ticket prior to boarding the train.
Your Florence to Venice ticket however cannot be changed, it is a 2 for 1 fare and completely non changeable non refundable