The Obitus Recentes page lists all recent Necrology items where the 'Date of Death' which has been entered is after a given cutoff date. To change the cutoff date, either consult the web developer, or (for editors with full administrative permissions) visit this page, and taking great care not to disturb any other setting, choose 'Filter Criteria > Content: Date of Death' (not 'Fields > Content: Date of Death'), click the link, in the popup box change the date, and click 'Apply (this display)'. This change is not permanent until the 'Save' button is clicked.
A similar operation is used to adjust the post date, which is used to catch entries with older date of death which have been added significantly more recently than the date of death.