Good idea. Just did that.
Date and number may have different “translations” (or say msgstr) in different locales. The example I gave is used in applications and the context would mark that translators can change the format according their usage of date format.
Honestly (the source code of) Indico is quite unfriendly at this point; not only in the html/js but also somewhere in the main programs. IIRC I have sent a pull request to Indico mentioning all those d-m-y or m-d-y format usage…
@fweng322, it may have been stated before, but there is legacy code lying around, from the time before i18n-awareness of the developers of Indico.
It is not trivial to write i18n-able code, but I think we are coming much closer to it. It needs patience or motivated contributions (PR) though …