When calling setProposalDate(null) on a content, a proposal date on "1911-03-12" is stored instead of removing or clear the value.

So as soon as a content is edited or validated, a proposal date to "1911-03-12" is set.

As a consequence, the search for content awaiting validation since X days returns all the content being edited or validated.
If alerts on contents awaiting validation is activate, it could send a lot of (wrong) emails !!