[3.12] gh-123445: calendar: Improve descriptions for day and month attributes (GH...

[3.12] gh-123445: calendar: Improve descriptions for day and month attributes (GH-123483) (#124501)

gh-123445: calendar: Improve descriptions for day and month attributes (GH-123483)
(cherry picked from commit 8447c933da308939b06e33544ca9abc9fc46aa8b)

Co-authored-by: Mat S <mscull@gmail.com>
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>
Co-authored-by: Eric V. Smith <ericvsmith@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>