I sent this to someone who mainly speaks Italian and there was confusion. Left is translated by Google as "sinistra" which is not what I want, haha. More like "partire" or "lasciare" but I'm unsure if these are the correct words.
- I have one year left: mi rimane un anno, mi resta un anno, ho un anno. Variants are mi rimane solo un anno (I have only one year left), mi rimane ancora un anno (I've still one year left) and mi rimane appena un anno (I have barely one year left). A more colloquial form is ce n'ho per un anno (literally I have enough of it for one year, it's akin to one year to go). Note that avercene is often used for the time left to live.
The form with the verb avere ("ho un anno") should be used with some modifier (ho ancora un anno), otherwise if you say ho un anno you seem to be saying you're one year old. It's still possible to misinterpret ho solo un anno as "I'm only one year old"; this isn't likely with ancora.
There are some special forms used in specific contexts: in the military you would say un anno all'alba - a year till dawn.
no man left behind: nessuno sarà lasciato indietro
one week left until exams: manca una settimana agli esami.