Plantronics Calisto 800 Series Date Codes This article pertains to Calisto Models 820, 820-M, 825, 825-M, 830, 830-M, 835, and 835-M. The Date Code is located on the label on the back of the speakerphone next to the word “Date,” and is formatted as MMM-YY. Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website