def older_message(m, lastm):
    """return true if m is older than lastm by timestamp"""
    atts = {'time_boot_ms': 0.001, 'time_unix_usec': 1e-06, 'time_usec': 1e-06}
    for a in list(atts.keys()):
        if hasattr(m, a):
            mul = atts[a]
            t1 = m.getattr(a) * mul
            t2 = lastm.getattr(a) * mul
            if t2 >= t1 and t2 - t1 < 60:
                return True
    return False
