The Publication data of a page is a property of the page tough its not treated like a field for the content types in sitefinity (News, Blogs, Events...). The main reason for this is there are no custom fields for pages.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items