Many older works have been published hundreds of years after composing. For classical and older music it is common to store information about when it was published. I'm proposing work attribute "first publication" to be added. It should be a date field but also freetext field is fine if dates aren't currently supported.

Publishing years for classical works are often mentioned on liner notes, Wikipedia and on imslp.org.

Examples how imslp.org store this information:

http://imslp.org/wiki/List_of_works_by_Carl_Philipp_Emanuel_Bach
http://imslp.org/wiki/Symphony_No.2,_Op.43_%28Sibelius,_Jean%29