DateTime#to_time

static VALUE
datetime_to_time(VALUE self)
{
    volatile VALUE dup = dup_obj(self);
    {
        VALUE t;

        get_d1(dup);

        t = rb_funcall(rb_cTime,
                   rb_intern("new"),
                   7,
                   m_real_year(dat),
                   INT2FIX(m_mon(dat)),
                   INT2FIX(m_mday(dat)),
                   INT2FIX(m_hour(dat)),
                   INT2FIX(m_min(dat)),
                   f_add(INT2FIX(m_sec(dat)),
                         m_sf_in_sec(dat)),
                   INT2FIX(m_of(dat)));
        return t;
    }
}