Yes, date/time defaults are another thing localised builds would have
set correctly. However if the other Japanese bugs could be fixed in the
tree I would assume it would be acceptable for them to stick with the
default prefs - this isn't by itself a compelling reason to create a new
distro, but just the sort of change that may as well be made if you are
already customising the build. I can't think of anyone who would say
"it's cool and all, and I'd definitely help them out with development -
but I had to change the time/date setting".
