I have build a event calender. Users create events and give them a starting date (custom attribute).
I also have a date nav block to show all events. The default date navigation sorts articles on publication date. I would like to sort events on the starting date (custom attribute) instead of the publication date of an event.

Is it possible to edit the default date_nav block to sort articles/ pages based on a custom attribute? Including the default functionality of opening and closing active month or article / drop down functionality.

Any help will be much appreciated.