Due to way SharePoint deals with Custom Columns, they can't be administered using features: Once deployed they are always active. To confirm that Highlighter has been installed successfully, you can either:
a) Check Central Administration: Under System Settings -> Farm Management -> Manage Farm Solutions, 'Pentalogic HTML Calculated Column' should be shown as 'Deployed'
b) Create a new column: 'Pentalogic HTML Calculated Column' should be shown as an option.
All editions of SharePoint 2007 and 2010 (including WSS/Foundation).
Unfortunately SharePoint Online prohibits the use of Custom Field Types such as the HTML Calculated Column.
Since HTMLCC is rendering HTML, there is no option to have a DateTime output. In order to display a date correctly, please use the TEXT function.