GoldSim's reporting periods feature allows you to generate period-based summary data (e.g. averages and cumulative amounts) to view at the end of a simulation. However, the results can only be viewed and not used for other calculations in the model. If you need period-based summary data for additional calculations in your model, you need to calculate these results manually.
This simple model shows how a vector constructor can be used to take a scalar time-varying quantity and 'split' it into individual quantities associated with different time periods. For example, a flow rate that varies daily over the course of one or more years could be 'split' into components associated with different months. What you would end up with is a vector of months where the flows at a given index location would be zero except in the month associated with that index (e.g. index 3 for March, or index 11 for November). In this form, it is then possible to calculate average flows, cumulative amounts, etc for specific months. The same could be done for year periods or other periods.
See also the following models that make use of this approach: Time Series Data Preprocessing, Monthly and Annual Summaries, Annual Reporting Summaries and Monthly Reporting Summaries.