def Measurement_timeofday_method_diff(self,probe):
    """
    Computes diff between time values and caches last time.
    """
    delta = 0
    
    if hasattr(self,'_last'):
        delta = probe.microsecondsSinceEpoch - self._last;
        
    self._last = probe.microsecondsSinceEpoch

    return delta