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_name_99 ( date VARCHAR, opponent_in_the_final VARCHAR, surface VARCHAR )

### Question ###
On what date did the opponent in the Toshiaki Sakai final play on a grass surface?

### Accurate SQL ###

SELECT date FROM table_name_99 WHERE opponent_in_the_final = "toshiaki sakai" AND surface = "grass"