fix(model): handle `true` timestamp fields correctly (#12580) (#12581)

Pedro Augusto de Paula Barbosa
2020-08-01T20:27:22-03:00

Co-authored-by: Pedro Augusto de Paula Barbosa &lt;papb1996@gmail.com&gt;
Co-authored-by: Vishal Sood &lt;vishalsood1995@gmail.com&gt;