Issues with Historical Date Addon

We have purchased the Historical Dates Addon, but are having some issues.

When choosing the date, the year only goes back to 2006. Also, after choosing a date with the datepicker, the date seems correct in the form field. However, after saving, the value has been transformed to something like ‘sept/em/be’ and an error about the date format appears.

As soon as the Historical Date Addon plugin is disabled, the dates go back to normal.

Also, is there a filter I can use to only display the year on the front-end?

Thanks,
Sky