In forms where a date is required, [month] - [day] - [year] fields are not localized.

It means:
a) Month names are always shown in English.
b) Fields order is MDY while in other languages is DMY.

A first review of code drives me to an smarty-pkp function called:
function.html_select_date.php

This function does the job and need to be reimplemented taking in consideration the locale of the user.

For a) Month names must be in a translation file.
An alternative solution for b) is hidding fields behind a popup calendar.

To reproduce, just visits http://yourMagazine/manager/createAnnouncement with a lang diferent than English.