The Zwift Desktop Application (ZDA) appears to have code to read the $LANG, $LANG_ALL, $LANGUAGE and other locale-related variables, but does not actually seem to use them.
This is especially relevant when trying to create .fit files that have the correct date settings, depending on the country/location of the rider. For example, in the UK, the .fit files should be named based dd-mm-yyyy, while in the US, that would be mm-dd-yyyy. Other countries have their own formats as well:
It may also be relevant for logs that are produced that contain parseable times, but do not respect the client system’s locale settings.
Thanks for all the great work you’re doing with Zwift! #RideOn!