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The 23rd century, defined in the Earth calendar as being from 2200 until 2299, was a period of expansion for the Federation, with humans and other founding species, such as Vulcans, at the forefront of exploration. The long-running conflict with the Klingons, begun in the 22nd century, was a major topic of this century's history, as was the rekindling of tensions with the Romulans. Of particular note were the voyages of the starship Enterprise and the careers of its long-serving command staff under James T. Kirk.

The notation Common Era ("Before Common Era") and Common Era ("Common Era") are alternative neutral notations for Anno Domini ("Before Christ") and Anno Domini ("anno Domini"), respectively.