都可以.主句用一般现在时和现在完成时都行.
例如：It is/has been three years since I joined the amry.
很高兴为你解答!
多谢你的问题!It's been a long time since I last saw a film,还是It has been a long time since I last saw a film对？it's been=it has beenit's=it is