J.15.12 Pragma Relative_Deadline

The expected type for a relative_deadline_expression is Real_Time.Time_Span. 

A Relative_Deadline pragma is allowed only immediately within a task_definition or the declarative_part of a subprogram_body.

For an implementation that supports Annex D, a pragma Relative_Deadline specifies the value of the Relative_Deadline aspect (see D.2.6). If the pragma appears in a task_definition, the expression is associated with the aspect for the task type or single_task_declaration that contains the pragma; otherwise, the expression is associated with the aspect for the subprogram that contains the pragma.