  In the scalar tensor gravitational theories Newton's constant G_N evolves in
the expanding universe. Likewise, it has been speculated that the acceleration
scale a_0 in Milgrom's modified Newtonian dynamics (MOND) is tied to the scale
of the cosmos, and must thus evolve. With the advent of relativistic
implementations of the modified dynamics, one can address the issue of
variability of the two gravitational ''constants'' with some confidence. Using
TeVeS, the Tensor-Vector-Scalar gravitational theory, as an implementation of
MOND, we calculate the dependence of G_N and a_0 on the TeVeS parameters and
the coeval cosmological value of its scalar field, \phi_c. We find that G_N,
when expressed in atomic units, is strictly nonevolving, a result fully
consistent with recent empirical limits on the variation of G_N. By contrast,
we find that a_0 depends on \phi_c and may thus vary with cosmological epoch.
However, for the brand of TeVeS which seems most promising, a_0 variation
occurs on a timescale much longer than Hubble's, and should be imperceptible
back to redshift unity or even beyond it. This is consistent with emergent data
on the rotation curves of disk galaxies at significants redshifts.
