Spock and Kirk with a 20th century accountant.

The 20th century was the awesomest century of them all, as evidenced by its tendency to pull all time-travelers into itself. For this reason, it was classified by the Federation Science Commission as a "temporal black hole." Strangely, this temporal phenomeon had a spatial dimension, as virtually all sliders were deposited on Earth.

All functional holodecks were required to contain no less than 12,047 programs and/or holonovels set in the 20th century at all times.