When Admiral Morrow says there isn't going to be any refet of the Enterprise because she is twenty years old. According to the Star Trek Cronology, the Enterprise was about thrity years old at the time. I know the Star Trek Cronolgy wasn't written back then but its still a mistake because the in the episode "Menageri" it was etablished that that Captain Pike cammanded the Enterprise for 11 years before Kirk took command. Add that to the first five year mission under Kirk's command, the two years of refeting, the second five year mission under Kirk's command, and the five years that it was used as a training vessle and you do not get 20. You get more like thirty.