J William Piggott wrote:
Is there a reason that the old tree structure is still being used?
Sure, inertia. Things move very slowly in the time business.
Does it break something to have 'right' and 'posix' as sibling directories?
Well, it does mean TZ='right/America/New_York' doesn't work any more, and one must use TZ='../zoneinfo-leaps/America/New_York' instead. So there is a compatibility issue there.
/usr/share/zoneinfo /usr/share/posix /usr/share/leaps
By default, the subdirectories are called 'zoneinfo' and 'zoneinfo-leaps', with 'zoneinfo-posix' being a symbolic link to 'zoneinfo'. Of course as you mention many distributions still do things the old way. E.g., Debian and Fedora both ship multiple copies of the 'posix' directory, which obviously takes far more disk space than the symbolic-link approach in the tz distribution. I don't think applications can rely on either directory structure per se. For example, Solaris puts the directory in a different place, under /usr/share/lib/zoneinfo, and does not ship a leap-second version at all.