This plugin is part of a set of plugins belonging to the socialwall course format. (https://github.com/synergylearning/moodle-format_socialwall)
This block is used to indicate any due dates for activities such as an assignment or quizzes that have been added to a course. It is very similar to the standard Upcoming events block (calendar_upcoming) but it would also display any alerts posted by the teacher with its date. Alerts are posts with a special flag normally sent by teachers by using the socialwall format for a course.