Four countries hoping to join the European Union took important steps forward on their membership quests Tuesday, in one of the bloc’s biggest enlargement moves in more than 20 years.

Intergovernmental conferences were being held in Brussels to ceremonially open or close negotiating tracks for the top four candidates to join the 27-nation EU: Albania, Montenegro, Moldova and war-ravaged Ukraine. But it could still be years before any of them join.

“We have not seen this in more than two decades. The last time, it was in 2002. This is a Super Tuesday for EU enlargement and Ukraine is part of it,” Enlargement Commissioner Marta Kos told reporters.

While holding four meetings in one day is a rarity, 10 countries – most of them from central Europe – joined the EU in 2004. Croatia, the last country to be welcomed into the world’s biggest trading bloc, joined in 2013.

Changing times force a change of policy