In Assassin's Creed III, the opening sequence identifies 1754 as the start of Haytham Kenway's story.
The year appears at the beginning of the game's first sequence, which follows Haytham in London before he travels to the American colonies. This opening establishes him as a major character before the narrative shifts to his son, Connor.
Haytham's section covers the early stages of his mission in the colonies, including his search for allies and his involvement in events that shape the later conflict. The game eventually reveals that Haytham is a Templar Grand Master, making the opening perspective deliberately different from a conventional Assassin-centered introduction.
The date should not be confused with the later year 1775, when Connor's main storyline begins against the background of the American Revolution. Assassin's Creed III spans several decades, so its title sequence and central campaign have distinct chronological starting points.