Fix and improve DateTimePlus documentation

This issue is being reviewed by the kind folks in Slack, #needs-review-queue-initiative. We are working to keep the size of Needs Review queue [2700+ issues] to around 400 (1 month or less), following Review a patch or merge request → as a guide.

FYI #24 still cleanly applies to 10.1 so removing credit for #33

@kkalashnikov you can test by clicking retest.

Points in #28 still need to happen.

Addressed #23.2
Here's the updated patch. Please review.

FYI if you’re only going to address 1 point and not attempt the others the ticket is not ready for review