Is it still impossible to change language on datepicker?
No, I got it working in Spanish, by sheer accident on a testpage. When I wanted to implement it on a production page, I couldn´t. Even copying the datepicker from the testpage didn´t work. I put in a support ticket and then it suddenly worked. In short, I have no clue how to get it working again. Testpage and prod page were inside same site, same settings (site lang/user lang set to spanish, browser set to spanish). SO if you got those settings right, try putting in a support ticket if it doesn´t work.
You can see it here in Spanish: https://www.fincalapenultima.com/guiadeines
Didn’t work. Contacted support :D. Thanks tho.