According to the
[documentation](https://nim-lang.org/docs/times.html#parsing-and-formatting-dates):
> Other strings can be inserted by putting them in `''`. For example `hh'->'mm`
> will give `01->56`. The following characters can be inserted without quoting
> them: `:` `-` `(` `)` `/` `[` `]` ,. A literal `'` can be specified with `''`.
So if you wanna print like that, your format string should look like this:
`dt.format("YYYY'.'mm'.'dd")`. Here's a working sample on the playground:
[https://play.nim-lang.org/#ix=2db8](https://play.nim-lang.org/#ix=2db8)
