A customer did a error when he open a fiscal year.
For the fiscal year 2014, the date for the first and last day and also the date of the periods were entered in 2015. And they did the opposite for the fiscal year 2015.
Is the KB871789 enough to correct this issue.
You should be able to adjust the fiscal year dates...You might have to make 2014 become 2016 temporarily so that you can adjust the 2015 year first...and then run a Financial reconcile to correct the summary figures.
Test it in a test company first.