Using a cookie to change content for repeat visits.
Cookies, CSS, PHP | Type: PHP
How to style a Google calendar in an iframe embedded on a page.
CSS, PHP | Type: CSS
Once you've established a date, display it as you like (see catholic fdn single-events.php for complex usage)
ACF, PHP, WP/CP | Type: PHP
Create a folder within wp-content/uploads that will contain uploads for each custom post type.
CPT, PHP, WP/CP | Type: PHP
Sometimes you need to turn a WP template tag into a PHP variable, so you can construct a proper bit of code.
PHP, WP/CP | Type: PHP