Section 5. The divisions of the housing court department shall always be open and the business thereof, or of a justice thereof, may be transacted at any time; but such business shall not, except as provided in section six of chapter two hundred and twenty, be transacted on Saturday or Sunday or on a legal holiday unless it relates to an application which, in the opinion of the justice to whom it is made, is of pressing necessity; provided, however, that, if the convenience of the public so requires, the courts shall be open for the transaction of business on such Saturdays, not legal holidays, and during such hours thereof as the chief justice of the housing court department may determine.