text: CREATE FUNCTION alter_timestamps() RETURNS void AS $$
  DECLARE
  	columns varchar[] := ARRAY['creation_date',
  	'modification_date', 'publication_date'];
  	col varchar;
  BEGIN
  	SET LOCAL timezone='UTC';
  	FOREACH col IN ARRAY columns
  	LOOP
  		EXECUTE format('ALTER TABLE articles '
  			'ALTER COLUMN %I TYPE timestamp with time zone',
  			col);
  	END LOOP;
  END;
  $$ LANGUAGE plpgsql;
  
  SELECT alter_timestamps();
  