JHelp - Wrong date on SNCF tickets!!
 

They are regular fare...how do I switch the date? There seems be only a cancel option...

At the train station or if you can cancel then perhaps you will be issued a refund and can repurchase?

If you have time, send it back where it came from. If not, go to first SNCF station or SNCF boutique where you can get and ask to change the date. With regular fare, there shoudn't be a problem, except, I hope the train you want to take is available.

What out canceling the order and issuing a new one?

They can be exchanged in one of the exchange machines on the train station platform. Slide old ticket in; new ticket slides out.