Up to 12 months from the date you arrive, as long as your overseas licence is current and you carry it with you. If the licence is not in English you must also carry an approved English translation. After 12 months you need a New Zealand licence, which for most countries means converting your overseas one (see the separate question on converting). The 12 months restarts only if you leave New Zealand for more than a year. Source: NZ Transport Agency Waka Kotahi — https://www.nzta.govt.nz/driver-licences/new-residents-and-visitors/driving-on-an-overseas-licence/