Returns a float!

Compare with Unix date command's "seconds since 1970-01-01 00:00:00 UTC" (watch out for the difference in leap seconds between actual UTC and Unix time and the difference between TAI and UTC).

?- get_time(T),float(T),process_create('/usr/bin/date',['+%s'],[]).
1604652321
T = 1604652321.0266113.

The naming is ... lousy

It should be an arithmetic function and it should be written:

T is the_time()

possibly

T is the_time_of(now)

which would make much more sense.

get_time(T) reads as

• "get_time is an attribute of T", or
• "Find me a T so that get_time(T) is true" (there is no such T, really)

There is also now/1 from the SICStus 3 compatibility library:

?- use_module(library(dialect/sicstus/system)).
true.

?- now(T).
T = 1604988027.