Hi Joe,

For that, you should right-click on the grid, then on the Display button
in the resulting dialog. (Or on the menu entry Display... Ticks, Grids, Etc.,
then on the 'grids' check-box; it'll get you to the same place.)

You'll see that you can select an epoch for the grids (or for each of the
other measurement markings). Select 'D', and you'll get grids in the epoch
of date.

In theory, this provides the useful ability to set up grids in one epoch
and other markings, such as ticks, in a different epoch. This really _is_
useful in the world of terrestrial mapping, where one often sees maps made
with a grid in one geodetic datum and ticks superimposed in a different datum,
whilst getting coordinates read out in some other datum. In reality, I'm
beginning to think it sows more confusion than light; I may switch to a
single epoch for cursor readout and for measurement markings.

-- Bill