I encountered this issue while trying to package IRAF for Nix.

IRAF uses a 1980 epoch internally, converting Unix timestamps via gmt_to_lst() in unix/os/zfinfo.c:

fs->fi_atime = gmt_to_lst (osfile.st_atime);
fs->fi_mtime = gmt_to_lst (osfile.st_mtime);
fs->fi_ctime = gmt_to_lst (osfile.st_ctime);

Files with timestamps before 1980-01-01 result in negative values. In pkg/cl/pfiles.c (lines 260-263), the check:

if ((pkg_ftime = filetime (pkg_pfile, "m")) <= 0) {
    mkpfilename (pkg_pfile, pkgdir, pkname, ltname, ".cl");
    if ((pkg_ftime = filetime (pkg_pfile, "m")) <= 0)
        cl_error (E_UERR, e_nopfile, ltname);
}

treats <= 0 as "file not found", causing valid .par files with pre-1980 timestamps to fail with:

ERROR: Cannot find pfile for task "..."

When can this happen:

• Nix: All files in /nix/store have timestamp 1 (1970-01-01 00:00:01 UTC) for reproducibility
• Old archives: Files from tapes/archives predating 1980
• Reproducible builds: Any other build system that normalize timestamps to epoch

This can probably be fixed by clamping the negative timestamps to 1 in unix/os/zfinfo.c.

fs->fi_atime = gmt_to_lst (osfile.st_atime);
if (fs->fi_atime <= 0) fs->fi_atime = 1;
fs->fi_mtime = gmt_to_lst (osfile.st_mtime);
if (fs->fi_mtime <= 0) fs->fi_mtime = 1;
fs->fi_ctime = gmt_to_lst (osfile.st_ctime);
if (fs->fi_ctime <= 0) fs->fi_ctime = 1;

This should ensure that files with pre-1980 timestamps are still recognized as existing.