Reason for +MANIFEST & +COMPACT_MANIFEST birthday of 1 Jan 1970

[Tatsuki Makino]

Yuet-nan Wong via freebsd-ports wrote on 2020/11/09 09:25:
>  Thanks Guido. Perhaps I should be explicit - why do +MANIFEST and +COMPACT_MANIFEST have a birthday of 1 Jan 1970 rather than the date/time it is actually created. Perhaps this is just another bug.

Those files are written by packing_append_buffer in
pkg-1.15.10/libpkg/packing.c.
But archive_entry_set_mtime is not used there.