able to change the chapter published date format.

[cassiefreak]

have options for mm/dd/yy, dd/mm/yy or yy/mm/dd

[jsmnbom]

I will not add an option to do this since AO3 operates using yyyy-MM-dd e.g. on the https://archiveofourown.org/admin_posts page, and I would rather have everything match up.