I think getting a copy of the entire repository with the git clone command is the best option. It allows you to keep up to date with the code. [There should be 'RO' button on the page I previously described. It executes the following: git clone git://git.code.sf.net/p/logwatch/git logwatch-git, where logwatch-git is the name of the directory. The problem with doing an individual service is that you need to know which scripts and configuration files need changing. Among the Logwatch files there is...
The current http-error script and configuration files in the git repository use the new date format you listed, and should also detect the [ssl:warn] statements. You can download it from sourceforge.net, under the git tab in the Logwatch project page: https://sourceforge.net/p/logwatch/git/ It gives different options for downloading, including git clone and downloading a zip file.
You may have an old version of Logwatch. The http-error script was updated for Apache 2.4 some time ago. There is no apache2 service in the default Logwatch. You might be looking for the http service. As for php, that service script has not been updated in a long time, and needs work.
[exim] Ignore office 365 connector disconnects, by Josh Soref
[secure] counting systemd-logind new logins; patch by Christian Mertes
[logwatch.pl] fixed base64 encoding; patch by Jan Synacek
[cron] Counting more SELinux context errors; patch by Christian Mertes
[logwatch.pl] added support for xzcat, by Stefan May