I downloaded MSFT historical data from Yahoo Finance a year ago and re-downloaded it today again. I turns our the two datasets are different.
E.g., today I got Adj Close of MSFT for 1986-03-19: 0.066604
In the dataset from a year ago, I got Adj Close of MSFT for 1986-03-19: 0.068892
These two numbers are very similar but not the same. Other numbers changed, too. What's the reason for this change of historical data?