Date fields automatically set to current date in Edit mode

Steps to reproduce: a user logs in the back-office and edits an object with date fields, but without changing them. Then he publishes the object.

Current result: All those fields are automatically set to the current date, even if he doesn't touch them. These field values are wrong.

Expected result: the date fields shouldn't have changed.

Remarks: Does not affect v2.5.13.