When is the last time the Catholic Mass was changed?

Depends on what you mean by "changes". The translations changes you're talking about haven't happened since the 1960's when the New Order Mass first came out with the English translation. However, there were other changes. The General Instruction of the Roman Missal (GIRM) is the main document explaining how the Mass is to be celebrated. There was a previous edition of the GIRM was released in 1975, then in 2000 Pope John Paul II released a new edition, which was slightly modified in 2002. Now countries with a National Conference of Bishop can petition Rome for approval of some changes. The US Council of Catholic Bishops (USCCB) submitted some national adaptations which were approved in 2003. And then the Vatican recently approved the USCCB submission for translation changes (which is what you're talking about). So that's a brief summary.

every other day. ha!