过去完成时与already，ever，just，never，“since＋时间点”，“for＋时间段”等连用时，强调事件发生的先后顺序，不涉及现在的情况。现在完成时强调的是“过去的动作或状态对现在造成的影响”。如：
She has worked in Chongqing for over two years.她已经在重庆工作两年多了。(现在仍在那儿工作)
She had worked in Chongqing for over two years before she moved to Shanghai.她在搬到上海之前已经在重庆工作两年多了。(“搬到上海”是过去，“在重庆工作”发生在过去的过去)
He has never seen such an interesting film before.他以前从未看过这么有趣的电影。(“看”尽管发生在过去，但涉及现在，即现在已经知道或了解了这部电影)
He said he had never seen such an interesting film before.他说他以前从没看过这么有趣的电影。(“他说”发生在过去，“看过”是在“说”之前，是过去的过去)