Bug: Timestamp property is not recognized. Trying to add an entity with this property generates an error 400.

[SebConejo]

My backend entity contains an entity with this property:

    - { name: aquiredAt, type: timestamp }    

From the admin panel, if I add or edit an item to this entity, I get a 400 error. A help text is saying The value must be a valid timestamp whereas I correctly filled the field.