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_204_959 ( id number, "club" text, "founded" number, "nickname" text, "location" text, "home ground" text, "entered competition" number, "most recent promotion" number )

### Question ###
what is the difference , in years , between the founding of the heidelberg football club and the eltham football club ?

### Accurate SQL ###

SELECT ABS((SELECT "founded" FROM table_204_959 WHERE "club" = 'heidelberg football club') - (SELECT "founded" FROM table_204_959 WHERE "club" = 'eltham football club'))