Steps to reproduce:
0. Start Liferay DXP 7.3-SP3
1. Login as Administrator.
2. Navigate to Menu > Content and Data > Form
3. Create new Form with a Date picker field in it.
4. Publish the new Form.
5. Navigate back to the Homepage
6. Change the site language to Hungarian in Control Panel > Instance Settings > Localization > Default language (if the context don't change, remove english as a available language as well)
7. Add an Form Widget to the page and set to display the new Form > Click Publish to save the Homepage layout.
8. On the Date Field of the Form click on the Calendar icon for the modal window.
Expected behavior: On the Modal window the Calendar starts from "Hétfő"(Monday) with the initial of "H" and it follows the Hungarian initials as: (H) K Sze Cs P Szo V.
Actual behavior: The Modal window has the layout as you can see on the attached screenshot that the customer provided (I can confirm the behavior).