x_axis_date=True,
            x_axis_format=LINECHART_X_AXIS_TICKFORMAT,
            height=chart_height,
            chart_attr=self.line_chart_attr,
        )
        tis = dag.get_task_instances_before(base_date, num_runs, session=session)
        for task in dag.tasks:
            y_points = []
            x_points = []
            for ti in tis:
                if ti.task_id != task.task_id:
                    continue
                dttm = wwwutils.epoch(ti.execution_date)
                x_points.append(dttm)
                
                y_points.append(ti.prev_attempted_tries)
            if x_points:
                chart.add_serie(name=task.task_id, x=x_points, y=y_points)
        max_date = max((ti.execution_date for ti in tis), default=None)
        chart.create_y_axis("yAxis", format=".02f", custom_format=False, label="Tries")
        chart.axislist["yAxis"]["axisLabelDistance"] = "-15"
        session.commit()
        form = DateTimeWithNumRunsForm(
            data={
                "base_date": max_date or timezone.utcnow(),
                "num_runs": num_runs,
            }
        )
        chart.buildcontent()
        return self.render_template(