Vendor import of tzcode2010a:

• asctime.c - Set errno to EINVAL and return "??? ??? ?? ??:??:?? ????\n" if asctime_r is called with a NULL struct tm pointer. (Note that asctime_r is called by ctime_r and asctime; asctime is called by ctime.)
• localtime.c - Set errno to EINVAL and return WRONG if time1 is called with a NULL struct tm pointer; avoid dereference if a NULL struct tm pointer is passed to timelocal, timegm, or timeoff. (Note that time1 is called by mktime, timegm, and timeoff; mktime is called by timelocal.)

Obtained from: ftp://elsie.nci.nih.gov/pub/