user: Question: When the Away team of Essendon played and the Crowd was larger than 18704 people, which Date did this take place on?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Collingwood', '21.23 (149)', 'Geelong', '11.13 (79)', 'Victoria Park', 49552.0, '21 April 1973']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Crowd" > 18704.0 AND "Away team" = 'Essendon';