XMLTV is an open source project that provides a standard way to format data for television schedules. The data produced by it is the source for many Electronic Programming Guides (EPG) that are used by TV programs. More on the XMLTV project home page.
mc2xml is one example of a program that can write XMLTV files.
J. River Media Center 13 and above can build an EPG by importing data in the XMLTV format.