The end day and conclusion time in the function in ISO-8601 format. Use exactly the same structure as startDate. Add both equally the date and time so users can find occasions that fit into their agenda. For online activities, you have to specify the timezone by such as the UTC https://www.presta-addons-modules.com/en/seo/prestashop-seo-automatic-google-rich-snippets-json-ld-opengraph-twitter-tags-schemaorg.html