The second step for the fix I’ve done in FEATURE: Don't show the 'Next Month' option in date pickers at the end of the month by AndrewPrigorshnev · Pull Request #15492 · discourse/discourse · GitHub.
That PR addresses date-time pickers on
- the bookmark modal
- the topic timer modal
This PR does the same job for other pickers (for example, for the picker on the slow mode modal).