Dollar Year is the year represented by the values in your Event. This is usually (but not always) the same as the year in which your event occurred or is expected to occur.
On the Impacts screen, Dollar Year should be the year of the data you are inputting.
On the Results screen, Dollar Year should be the year of which you want to report your results.
This should not be confused with the Data Year which is the year of the dataset that you are utilizing.