Assuming you do mean a gTLD ( com net org etc) rather than a ccTLD (country specific) then the transfer process is governed by ICANN and you will always have +1 year added to whatever the current expiry date is.
The only exception to the rule is if you already have more than 9 years on the domain. The maximum amount of time a domain can be registered for is 10 years, so the transfer will just complete as normal without the addition of another year.
There are also some discrepancies around transferring your domain JUST after paying for the renewal at the current registrar whereby the first renewed year would be rolled back and when the domain transfers you would end up with an expiry date 1 year in the future instead of 2. But that's pretty rare :)