Magento – How to translate Magento validate.js error

Try to add translation part in locale file:

magento\app\locale\YOUR PACAKGE(like en_EN,fr_FR)\Mage_Core.csv

It will reflect when it will translating message. I have work with this so.

The problem comes from a core bug.

See js/varien/js.js around line 450:

...
} else if (!day || !month || !year) {
    error = 'Please enter a valid full date.';
} else {
...

See the problem? It's the period ., which does not appear in the CSV, so the translation is missed every time. The easiest solution is the edit this file directly, removing the period so that translation works again... but of course, modifying core is not best practice.

Long Solution

If you have a generic local code pool module on your system, add or edit its jstranslator.xml file, and add this:

<?xml version="1.0"?>
<jstranslator>
    <!-- js.js -->
    <validate-date-full-date translate="message" module="rootd">
        <message>Please enter a valid full date.</message>
    </validate-date-full-date>
    <!-- end js.js -->
</jstranslator>

Here we should effectively overwrite the entry for this message that was originally defined in app/code/core/Mage/Core/etc/jstranslator.xml, and include the period which core code expects according to js/varien/js.js. Then, you can add an entry to your CSV:

"Please enter a valid date.","Your translation here"