Change period start date: Enter key doesn't send form

When changing the period start date and pressing enter (on the keyboard), the form is closed but the data is not correctly sent to the backend.

When using mouse click (submit button), it works as expected

Start by reproducing the period start date form submission with the Enter key and compare it with clicking the submit button. Trace the form's submission entry point and verify that the backend receives the same data in both cases; done means Enter closes the form only after the updated date is correctly sent.

Written by the indexing model from the issue text.