[schema] Use TZDatetime for creation_date and modification_date
No work has been done for form fields/widgets since creation_date /
modification_date are by default not editable through the default UI. One may
want to add such feature at some point.
Time will be displayed as UTC, let the end-application decide otherwise by
customizing the tzdatetime printer if desired.
Closes #4848923
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/index.html
Files: /usr/share/doc/cubicweb-documentation/*.html