A newly created Page does not Display
So continuing from the comments above.

You are calling theme('similetimeline', $html);, which in turn will call theme_similetimeline($html). So the main reason you don't get any output, is simply that you lack the theming function.

To get started, you can do away with theme() all together and just print $html;. Especially since you've already generated the markup, but on the other hand, it's great that you've already gotten far enough to know you should use theme(), considering you say you are a beginner. The reason for theme calls, is that you can separate the module and it's functionality, from it's markup, meaning this timeline can look different in different themes.

You will find a more extensive example, and a great answer by Clive, in a similar question I asked recently.