The 2017 school holidays calendar has been officially released by the MOE. You can check all the dates by scrolling down, remembering to look at your correct table (whether Kumpulan A or Kumpulan B).
The dates below are from the MOE website, so are considered the official school holidays dates for 2017.
Kumpulan A Schools 2017 (Johor, Kedah, Kelantan, Terengganu)
Kumpulan B Schools 2015 (Kuala Lumpur, Labuan, Melaka, Negeri Sembilan, Pahang, Perlis, Penang, Perak, Putrajaya, Sabah, Sarawak, Selangor)
Visit moe.gov.my for the original release 2017.