Popup calendar/First date of week

krileon wrote: As a feature to what? The feature already exists. By default it's not supposed to be used and uses whatever jQuery UI has been defined with. That usage overrides jQuery UI.

If 'UE_CALENDAR_FIRSTDAY' => '0', would be present in default_language/language.php
it would also be translatable in Transifex to make the popup calendar display correctly in localizations by default and without overrides.
Like 'UE_CALENDAR_FIRSTDAY' => '1', in sv-se/language.php for monday first in Swedish calendar.

If that was set then if someone was using their own jQuery they'd lose whatever their jQuery was set to use as default. Language also doesn't necessarily mean location as well. I think it's best if it's kept as a manually specified usage and not something forced on everyone when using language plugins.