I didn't write the app that does the differencing.  It expects a float in seconds from the using program, so that means floating this:

(/ (get-internal-real-time)(internal-time-units-per-second))


In ACL (get-internal-real-time) is several orders of magnitude smaller than what ABCL returns...
bonasso <bonasso@traclabs.com> writes:

I solved this by coercing 
(get-internal-real-time)
into a double float.

Looks like the epoch start time for these functions is different from
lisp to lisp.

ACL: (get-internal-real-time) => 8456209511
ABCL: (get-internal-real-time) => 1401814359707

Does anyone know the date from which the value for
(get-internal-real-time) is computed for abcl?
Why do you need to coerce it to anything for intermediate values?
Store the value returned by (get-internal-real-time), then subtract it
from another (get-internal-real-time), only then divide it by
internal-time-units-per-second, and only then, if you need to, convert
that into floats, for printing or something. That way you will lose
minimal precision.