Trying to redefine imported existing procedure in ground/1

Hi,

I'm very green to Eclipse 5.8 and trying to solve little puzzles which 
involve Allen's intervals (like the one in K. Apt's book). The user 
manual 8.2 suggests doing

:- lib(chr).
:- chr2pl(time).
:- ['time'].

this dies with 'calling an undefined procedure'. Later on 8.2 suggests
:- chr(time).

but this also dies. At some point, I was getting error messages about 
ground/1 being redefined in 'time-pc'. Further investigation showed that 
chr has been phased out in favour of ech, but then I have no clue how to 
get the functionality of old chr under ech...

Would somebody please put me out of my misery with an example how to 
work with Allen's intervals?

Help, pointers, examples are much appreciated.
Thanks, Laszlo