That regexp is the best heuristic we could come up with that caters to
the various formats of date and time that the various versions of 'ls'
out there produce.  It is true that the regexp can be tricked into
mistakes, but we could not find a better solution that supports all
the valid use cases.  We use the --dired option of 'ls' when available
precisely for this reason: to allow Dired to determine the file names
reliably.  If --dired is not supported, then there will be problems
with certain file names, yes.  That is a known limitation, so users
are encouraged to install GNU Coreutils (which is where GNU 'ls' comes
from) to make Dired immune to those problems.