When did the states of Mizoram and Arunachal Pradesh come into being?

The states of Mizoram and Arunachal Pradesh were formed in the year 1987.

1987: Arunachal Pradesh- Arunachal Pradesh became a Union territory in 1972. In February 1987 it became a full-fledged state of India.

1987: Mizoram- In 1972 the Mizo hills became a Union territory of India. It was elevated to the status of a full state in 1987.