是seems还是seemed? 请网友注意书写。

It seems that... 常可转换成“名词或代词＋seem＋不定式”结构，意义不变。如果不定式为to be＋形容词，to be可省略，但要注意时态。比较：

It seems that he is ill. = He seems (to be) ill. 他好像病了。

It seems that he was ill. = He seems to have been ill. 他好像生过病。

▲你的问题中的seemed是过去时态，但同样可以据此反推。即：

It seemed to be a long time. = It seemed that it was a long time.  似乎时间很长。

It seemed to have been a long time. = It seemd that it had been a long time.  好像过了很长时间。

（上面两个简单句变为复合句之后，第一个it都是虚拟主语，第二个it都是作that从句中的主语，表示时间）