Star Trek TOS → “City on the Edge of Forever”

Capt. Kirk: [narrating] Captain’s log, no stardate. For us, time does not exist. McCoy, back somewhere in the past, has effected a change in the course of time. All Earth history has been changed. There is no Starship Enterprise. We have only one chance. We have asked the Guardian to show us Earth’s history again: Spock and I will go back into time ourselves and attempt to set right whatever it was that McCoy changed.