When TNG came along somebody - presumably Gene himself - decided to have a much more sensible, logical system of Stardates. To show that the new series was set later on than the original, all Stardates were five digit numbers rather than four. The first digit was a four, since the show was set in the 24th century. The next digit was a 1 since it was the first season of the show. And every season was a new year on Earth. And towards the end of the first season, Data gave us the year as being 2364.

Data states Admiral Dr. McCoy's age at being 137 (see 1st season TNG: Encounter At Farpoint - 2364).

• McCoy was born between 2226 or 2227.

In the 6th season of TNG was revealed in the sickbay scene, that Scotty would be 147. TNG: Relics is set in 2369:

• Scott was born someday in 2222. In this situation you are not long calculating about days and month. You just think "I was born 2222. Now it is 2369. Therefore I am a 147 year old man!"

Ambassador Sarek of Vulcan was 202 years old when he made an appearance in "Sarek" (TNG's third season, or 2366).

Sarek was born in (2366-202=) 2163 or 2164 (depends on his birthday)

Sarek was 102.437 years of age when he appeared in "Journey To Babel", TOS second season. This was 100 years before TNG's third season, and therefore took place between 2265 and 2266.