FYI, here is another important note I feel on how stars are dated. "The evolutionary track that a stellar model traces in an HR diagram is somewhat code dependent. Many stellar evolution codes are currently being used, and they produce different results in part due to uncertainties in the input physics (such as the opacity, the equation of state, and the nuclear reaction rates),…", Ref - p. 511, Allen's Astrophyscial Quantities, Fourth Edition, 2000. My note. The ZAMS equation of state and nuclear reaction rates for the Sun were fixed using radiometric age of meteorites in mid-1950s when Clair Patterson studies fixed the age of the Earth, Sun, and solar system. This ZAMS plot for the Sun is used to model the Faint Young Sun and other star clusters HR plots too.