The template goes into the display variable, which is JSON encoded. You can see what it should be by looking at the OPF for a book in your library. One example is
Code:
{"composite_template": "{:'approximate_formats()'}",
"contains_html": false,
"make_category": true,
"composite_sort": "text"
}
I strongly recommend that you look at the OPF because there are several fields that can play a role.
Regarding date formatting, this is also a JSON-encoded string. One example is
Code:
{ "date_format": "yyyy/MM/dd" }