It must accept the "." as a standalone date formatting character.
function eval_fmt(fmt, v, opts, flen) {
...
default:
- if(",$-+/():!^&'~{}<>=€acfijklopqrtuvwxzP".indexOf(c) === -1) throw new Error('unrecognized character ' + c + ' in ' + fmt);
+ if(".,$-+/():!^&'~{}<>=€acfijklopqrtuvwxzP".indexOf(c) === -1) throw new Error('unrecognized character ' + c + ' in ' + fmt);
+ // ^^^ Allow "." for Hungarian date format: yyyy.mm.dd.