How long to learn HTML5, CSS, php, JS, etc?

[eclipse]

Hi all,
If I was to dive in as an amateur developer interested in designing and manipulating CMS's like Joomla and Wordpress, how long would it take to learn:

HTML5

CSS

PHP

JS?

Or would I just mainly be doing HTML and CSS and relying on forum support for the occasional PHP tweak? I'm mainly interested in being able to design websites in CMS, not completely reprogram the php I guess. Any estimates out there as to how long it takes to get a 'good' understanding of these languages?

Cheers