The more I look into this the more I can't find solid evidence that TOS takes place in the 23rd century. Khan is told in Space Seed and states in TWOK that he was in power 200 years prior. In Savage Curtain Lincoln is said to have died 300 years prior. When Kirk is threated with being locked up for 200 years in Tomorrow is Yesterday he considers that enough time to get back to his own era. This all points to TOS being in the 22nd century. The only time I can think of where "23rd Century" is said in TOS is in TVH. Is there any other proof of this within TOS (not the later series)?