At what date and time did San Jose Diridon Caltrain Station have most bikes available.
San Jose Diridon Caltrain Station is the name of the station; most bikes available refers to MAX(bikes_available);
SELECT T2.time FROM station AS T1 INNER JOIN status AS T2 ON T2.station_id = T1.id WHERE T1.name = 'San Jose Diridon Caltrain Station' AND T2.bikes_available = ( SELECT MAX(T2.bikes_available) FROM station AS T1 INNER JOIN status AS T2 ON T2.station_id = T1.id WHERE T1.name = 'San Jose Diridon Caltrain Station' )