I cribbed a command intended to make an exact copy of files to another directory
tar cpBf - . | (cd <target directory>; tar xBf -)
and stupidly did not check it against the man page. Regards the p option the man page says "p, --same-permissions, --preserve-permissions. ignore umask when extracting files (the default for root)
". Thus the p option is undefined when used with the c (create) option; it is only defined in conjunction with the x (extract) option.
The source directories (/etc/rc.[0-6S].d in turn) contain symbolic links and an ordinary file. After running the command, the modification times on all the symlinks was reset to the time the tar command was run; the ordinary files had the original modification time.
How did that happen?!
That's what backups are for
c@CW8:~$ tar --version
tar (GNU tar) 1.19