HTML-Calendar is a Scripts software developed by gerd tentler. After our trial and test, the software is proved to be official, secure and free. Here is the official description for HTML-Calendar:

BSEditor: Use this Python class to create a monthly calendar. It's easy to use and highly customizable, supports multiple languages, and you can choose whether weeks start with Saturday, Sunday, Monday, or any other day. Of course you can create as many calendars as you like. Have a look at the example below. It shows five calendars; the current month (big in the Middle) plus the two previous months (left) and the two next months (right)