$ mkdir d
$ cd d

$ whoami
> root

$ touch a b
$ sleep 1

Without write access, the ctime cannot be changed.
	$ su bin
	$ touch a
	> touch: cannot touch `a': Permission denied

With write access, the ctime can be set to the current time, but not to
any other time:
	$ su
	$ nfs4acl --set 'bin:rw::allow' a

	$ su bin
	$ touch a
	$ [ b -ot a ] || echo 'b should be older than a'
	$ touch -r b a
	> touch: setting times of `a': Operation not permitted

With set_attributes access, the ctime can be set to an arbitrary time:
	$ su
	$ nfs4acl --set 'bin:rwt::allow' a

	$ su bin
	$ touch -r b a
	$ [ b -ot a -o a -ot b ] && echo 'a should be as old as b'

$ su
$ cd ..
$ rm -rf d