In which year did North Yemen and South Yemen unite?

Yemeni unification took place on May 22, 1990, when the area of the People's Democratic Republic of Yemen (also known as South Yemen) was united with the Yemen Arab Republic (also known as North Yemen), forming the Republic of Yemen (known as simply Yemen).

Ali Abdullah Saleh of the north became Head of State, and Ali Salim al-Beidh became Head of Government. A 30-month transitional period for completing the unification of the two political and economic systems was set. A presidential council was jointly elected by the 26-member Yemen Arab Republic advisory council and the 17-member People's Democratic Republic of Yemen presidium. The presidential council appointed a Prime Minister, who formed a Cabinet. There was also a 301-seat provisional unified parliament, consisting of 159 members from the north, 111 members from the south, and 31 independent members appointed by the chairman of the council.