Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_30731 ( "Institution" text, "Nickname" text, "Location" text, "Founded" real, "Joined ACC" real, "School Type" text, "ACC Football Titles" real )

### Question ###
when did the institution at chapel hill, North carolina join acc?

### Accurate SQL ###

SELECT "Joined ACC" FROM table_30731 WHERE "Location" = 'Chapel Hill, North Carolina'