Why the need to validate tickets?

I cannot understand the reason for requiring tickets to be validated before you get on the train - do you know what it is? T.B.

The SNCF admit that having to validate rail tickets is unfamiliar to people from other countries, however they claim their system allows for more flexibility. Unlike in most countries where a ticket is for the day of purchase, ordinary unreserved tickets are valid for up to two months.

However to avoid abuses (ie. a person using the same one several times) it is necessary to punch it with the date before getting on the train.

Technically, they say, punching it is like the final signature on your contract to buy a journey on the train you are on and you are not an official passenger until you have done it.

Not doing so would also mean they would take no legal responsibility in relation to you or your trip.

If you forget, you are meant to present yourself spontaneously to the train conductor to let them know. Being caught with one unpunched can lead to a fine.