  Although the means of the ages of stars in young groups determined from Li
depletion often agree with mean ages determined from Hertzsprung - Russell
diagram isochrones, there are often statistically significant differences in
the ages of individual stars determined by the two methods. We find that
inclusion of the effects of inhibition of convection due to the presence of
magnetic fields leads to consistent ages for the individual stars. We
illustrate how age consistency arises by applying our results to the \beta
Pictoris moving group. We find that, although magnetic inhibition of convection
leads to increased ages from the Hertzsprung - Russell diagram isochrones for
all stars, Li ages are decreased for fully convective M stars and increased for
stars with radiative cores. Our consistent age determination for the \beta
Pictoris moving group of 40 Myr is larger than previous determinations by a
factor of about two.
