Do we know what year Phase II was supposed to be ? 23rd or 24th century?
At that point, they hadn't tied down the specific years when
Star Trek took place; it wasn't until TWOK that it was definitively established as taking place in the 23rd century, and it wasn't until the end of TNG's first season (in "The Neutral Zone") that we got a specific calendar year for any Trek episode or movie. (Roddenberry didn't want to tie down the date too precisely. TWOK did it because Roddenberry was only a consultant there, and "The Neutral Zone" did it because it was shot from a first draft during a writers' strike, otherwise the date reference might've been cut.)
But
Phase II was meant to be set just a few years after TOS, reuniting all the TOS cast except for Spock aboard a refitted
Enterprise on its second 5-year mission. Remember, TMP was a rewritten version of the pilot script for
Phase II, so that series would've been in the same basic timeframe as TMP.