Tomorrow is Yesterday - S1-E20
Corrected entry: When the Enterprise is slingshotting its way back to the "present" it uses the computer to deposit the two men at different times, The Enterprise is traveling backwards in time, so will logically meet the time when the guard was beamed up first, not after Christopher is returned to his cockpit. So the order is wrong. Should be guard then Christopher, not Christopher then guard. (00:43:15)
Correction: They are moving backwards in time as they approach the sun, but after the slingshot breakaway they are moving rapidly forward in time. Spock even says the chronometer is moving forward again, and then Kirk asks if they have the exact chronometer reading before redepositing Captain Christopher and the Sergeant. So the order depicted in the episode is actually the correct order.