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_6555 ( "Task No." real, "Day announced" text, "Options" text, "Viewers' selection" text, "Result" text )

### Question ###
when was it announced that the viewers selected robi out of alex, ejay, nan, robi?

### Accurate SQL ###

SELECT "Day announced" FROM table_6555 WHERE "Viewers' selection" = 'robi' AND "Options" = 'alex, ejay, nan, robi'