Problem/Motivation
This is a very minor inconvenience, but I noticed while creating a new date time format at /admin/config/regional/date-time , that the link to the php.net documentation of datetime formats is less than ideal. Currently it takes you to: https://www.php.net/manual/en/function.date.php This page does not actually have the formats table the user will be looking for. I believe it should take you here instead: https://www.php.net/manual/en/datetime.format.php
Searching the Drupal core codebase for "https://www.php.net/manual/en/function.date.php" reveals that this is an inconvenience in multiple places throughout core.
Proposed resolution
I propose we replace all links to https://www.php.net/manual/en/function.date.php with https://www.php.net/manual/en/datetime.format.php
