Please upgrade to 2.1.x here.
The 2.0 branch is no longer being updated.
I assumed that the 'Locale' configuration setting was used for HTML and HTTP locale information. I changed that local configuration in config.php
$Configuration['Garden']['Locale'] = 'en-US';
but it appears that 'en-CA' is still being used, for example in the HTML element
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-ca">
Is en-CA hardcoded?