let mut buffer: &mut [u8] = &mut [0u8; 8];

        let mut buffer = [0u8; 8];

            .format_into(&mut buffer, format_description!("[day][month][year]"))

            .format_into(
                &mut buffer.as_mut_slice(),
                format_description!("[day][month][year]"),
            )

        f.write_str(core::str::from_utf8(buffer).expect("valid UTF-8"))

        f.write_str(core::str::from_utf8(&buffer).expect("valid UTF-8"))