How to check out a project based on commit time rather than rev?

Obviously this is a "for dummies" question but I *have* looked at the
svnbook but I cannot still find how to do this:

An old project suite has been converted from CVS to SVN and now we
need to go back in time in SVN and get a version that was current at a
time like 2017-01-01.
There are several project directories that have been modified at
different times because they hold different software components.

But AFAICS there is no checkout alternative that makes it possible to
use a timestamp, only revision numbers....
For svn log I found that one can use -r {2017-01-01}, is that possible
also for svn co?
But unfortunately even for log it returns an empty dataset when I do:
svn log -r {2017-01-01}

I have no idea how to find a relevant revision number for a date
inbetween two commit dates so I can use it as a revision to define the
state of the projects. And if I found one, what happens if a file was
not committed in that revision, will it still appear in the checkout?

Alternately I could also copy the state at this time to a tag, but I
still need to know a revision number for that and all I can say is
that it should be before a certain time.

I use svn 1.9.7 on both client and server.

-- 
Bo Berglund
Developer in Sweden