It looks like this template is a custom template that you had created at some point (you can see it says custom under the heading on the left).
It looks like this template may have been using “Timestamp” relative calendar style, where instead of dates, events are given a time offset from a specific position (eg. 0:00:00). It just happens that this has opened at a bad default location (very negative time). If you go to Navigation->Scroll to Time, you can enter at better time (eg. 0:00) to scroll to.
This type of template is useful for instances such as Screenwriting, where people might want to timeline where each event happens during the actual time of the movie/tv show.
You can delete custom templates you do not want under via Tools->Options (Windows) or Aeon Timeline → Preferences (Mac). Clicking the Custom Templates tab will then give you a list of all your custom templates, of which you can choose which ones to delete.
