Dear Dario,

Errrmmm... yes, Guide _does_ look at the header and
determines the valid time span accordingly. It really
has little choice in the matter. The time spans you mention
are only correct if one uses a complete DE file; there are
plenty of "sub-DE" files out there covering assorted smaller
spans (including some on the Guide CDs.)

Have you found cases where Guide ought to be using DE
(that is, you've told it to look at a DE file covering
the correct time span), but found that it reported using
VSOP or ELP or PS-1996 in 'More Info'? For which planet
and date(s) and time(s) and ephemeris file(s)?

-- Bill