According to the newspaper Mundo Deportivo
The next Clásico between FC Barcelona and Real Madrid will be played next Saturday April 2, at 8.30 pm CEST. The date and schedule was published by the newspaper Mundo Deportivo, where it's also said that La Liga will officially publish the date next week.
Both teams will probably play Champions League around that dates. The first leg of the quarterfinals will be on April 5 and 6. Barcelona and Madrid have many options to be there so this is one of the reasons for El Clásico to be played on Saturday and not on Sunday.