A chronotropic fragment was an anomalous type of computerized data, created by manipulation of the timeline. In 1969, the Beta 5 computer detected a chronotropic fragment in its memory banks which correlated to no other data, and was thus deleted. This fragment had been created when Gary Seven and Roberta Lincoln traveled back in time with the USS Enterprise, and prevented their past selves from interfering with the re-insertion of Captain John Christopher into his F-104 Starfighter. (TOS - Star Trek: Assignment: Earth comic: "Yesterday, Today and Tomorrow")