def GetStepStartAndEndTime(build, full_step_name):
  """Gets a step's start_time and end_time from Build.

  Returns:
    (start_time, end_time)
  """
  for step in build.steps or []:
    if step.name == full_step_name:
      return step.start_time.ToDatetime(), step.end_time.ToDatetime()

  return None, None