it has been a long time since..和 it's a long time since..和 it's been a long time since..

Question

上面这三种说法有什么区别吗？还是说他们的意思都一样可以随意用

Answer 1

it's been a long time since.. = it has been a long time since..
it's been 是 it has been 的缩写

it's 也可以是 it is 的缩写
it's a long time since.. 就变成了 it is a long time since ...

在语法上是不对的，后面是since，要用上面的 it has been 才对。追问

那It's a long time since I've used it. 这样对吗？是不是强调了当时的情况

追答

It's been a long time since I used it.
我已经用了它好长一段时间了。
后面用过去式，前面用 has been, 表示现在还用着。