When did missions start and end?

Missions, particularly in the context of Christian missionary work, began in earnest in the early centuries of the Common Era, with significant expansion occurring from the 15th century onward during the Age of Exploration. The establishment of missions continued through the colonial period, peaking in the 19th century. While many missions still operate today, the traditional model of mission work has evolved, and the concept of missionary activity has shifted significantly in the 20th and 21st centuries. There is no definitive end date, as missionary work continues in various forms around the world.