Who Can Alter A Package Body

ALTER PACKAGE BODY APP_VAR
AS
BEGIN
  - Returns the start date of the period
  FUNCTION GET_DATEBEGIN() RETURNS DATE DETERMINISTIC
  AS
  BEGIN
    RETURN RDB$GET_CONTEXT('USER_SESSION', 'DATEBEGIN');
  END
  - Returns the end date of the period
  FUNCTION GET_DATEEND() RETURNS DATE DETERMINISTIC
  AS
  BEGIN
    RETURN RDB$GET_CONTEXT('USER_SESSION', 'DATEEND');
  END
  - Sets the date range of the working period
  PROCEDURE SET_DATERANGE(ADATEBEGIN DATE, ADATEEND DATE)
  AS
  BEGIN
    RDB$SET_CONTEXT('USER_SESSION', 'DATEBEGIN', ADATEBEGIN);
    RDB$SET_CONTEXT('USER_SESSION', 'DATEEND', ADATEEND);
  END
END