When you are using versions, the switchover date is the date at which your actuals become forecasts. For example, if you are looking at a module where time is a dimension, and you have actual sales recorded through March, 2016, your switchover date would be April, 2016. Any values seen in the months January, February, and March would be what was actually sold, and any values in April and beyond are what is forecasted to be sold.
