§1. To be valid, a novitiate must include twelve months spent in the community itself of the novitiate, without prejudice to the prescript of can. 647, §3.
§2. To complete the formation of novices, in addition to the period mentioned in §1, the constitutions can establish one or more periods of apostolic exercises to be spent outside the community of the novitiate.
§3. The novitiate is not to last longer than two years.
Source: Code of Canon Law (Vatican.va)