jelleS

Problem:
The client is experiencing an issue where dates on their Swiss French language version of the site do not translate correctly and revert back to English. This occurs because WordPress does not officially support the 'fr_CH' locale, causing a fallback to English for core date strings.
Solution:
To resolve this, we recommend either manually copying the official French WordPress translation files ('fr_FR.po' and 'fr_FR.mo'), renaming them to 'fr_CH.po' and 'fr_CH.mo', and uploading them to

wp-content/languages/

. After clearing all caches, WordPress will automatically load these files, and the

date_i18n()

function will render French month names correctly on the Swiss French site.
Alternatively, using the Loco Translate plugin to create a French (Switzerland) 'fr_CH' translation for WordPress core (based on 'fr_FR') and translating the date strings there can achieve the same result without manual file handling and is safe across updates.

Please note that these files will not be removed by a WordPress update as the 'wp-content/languages/' directory is meant for custom and downloaded translation files and is not affected by core updates. However, since 'fr_CH' uses 'fr_FR' as a fallback, it won’t automatically receive updated translations when French translations are updated. If new strings are released, you would need to re-copy the updated 'fr_FR' files again.

If this solution does not resolve your issue or seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If the problem persists, please open a new support ticket at WPML support forum for further assistance.