"Trying to find birthdate of Josiah Harding"
This Might Help: FamilySearch.org
This MIGHT be him but one can never be too certain:
"married Lucinda myrick on vinalhaven in 1820"
Cannot firm this via FamilySearch of Maine Vital records. This is as close as I got: FamilySearch.org
You can consult this page: Vinalhaven Genealogy Resources & Vital Records | Knox County
Or you can contact the Maine Historical Society: MHS Discussion Board
thank you. i didn't add enough info. according to census reports he was born around 1797.