last - year是什麼詞性

詞性是名詞短語，例如：

1、Who could forget his speech at last year's party?誰能忘記他去年在聚會上的講話呢

2、The house came on the market last year.這棟房屋去年就上市了。

3、This year's results are virtually the same as last year's.今年的結果幾乎和去年的一樣。