In my experience, the "timezone" variable on USG systems is always positive -- that is, application code subtracts its value from the current time, rather than adding it. I have supplied a diff for localtime.c so that if USG_COMPAT is defined, the value of the global "timezone" variable is forced positive. This is based on observations of Plexus System 3, Xenix System 3, and Xenix System 5. I don't know how USG would treat negative offsets from GMT. Observations presumably not made in Europe. You are correct in that the sign of the "timezone" variable should be positive for time zones such as those in the Western Hemisphere; however, it is not correct to force the offset to be positive, as there are places where the offset simply *isn't* positive (using the UNIX sign conventions). The correct fix is 182c185 < timezone = s.ttis[0].tt_gmtoff; --- > timezone = -s.ttis[0].tt_gmtoff; 197c200 < timezone = ttisp->tt_gmtoff; --- > timezone = -ttisp->tt_gmtoff; or something like that.