def get_oldest(fromlist):
  """
  get_oldest(fromlist) where fromlist is a list of DataObjects
  Get the oldest timestamp out of all the timestamps in the DataObject list.
  """
  oldest_timestamp = fromlist[0].data[0][1] #take the first timestamp from the first DataObject in the fromlist list
  for obj in fromlist:
    if obj.oldest_sample < oldest_timestamp:
      oldest_timestamp = obj.oldest_sample
  return oldest_timestamp