The Economist’s commodity price index is broadly unchanging from a year ago这个句子中from year ago是什么用法，我感觉有一种相比一年前的意思，和since a year ago用法一样吗？

On an adjusted basis Disney posted earnings of 60 cents a share, down 63 per cent from a year ago and well below Wall Street forecasts for 89 cents a share这里的from a year ago又是什么用法