During my first few years in the Unix room (starting in 1988) there was what seemed
like a semiannual flurry of leap year corrections made to research unix. Apparently,
there
was some aspect that kept misbehaving, with new bugs appearing at the next shift in time.
I never bothered to investigate the specifics, but it happened over several years. There
are
probably some on this list who know more details.
I don’t recall this being a problem on Plan 9.
ches