[3.12] gh-101100: Fix datetime reference warnings (GH-114661) (GH-114716)

(cherry picked from commit e8b8f5e9c2da6a436360ce648061c90bdfcba863)

Co-authored-by: Skip Montanaro <skip.montanaro@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>