As an experiment and exercise in how HTML5's <canvas> tag works, I did the below Canvas Clock tutorial found on the W3 Schools website.
The tutorial was very easy, and by doing it, I am not saying I know and understand exactly how the HTML5 <canvas> tag works on the production side of a website or when and how it is used by big advertising firms to serve ads on peoples' iPhones or Android devices, but I did learn a few things from the tutorial. Note: HTML5 Clock tutorial and demo