I am working on creating a sales summary for 299 with time along my columns and see that the unit price of products changes over time, as such I would like to create a formula that selects price data dependent on the current time period, e.g., if it's currently January 2017, price of good A should be Z and if it's currently July 2017, price of good A should be W. I've looked into the time formulas to find what I am looking for but have come up empty.
This works for you: Source Module.Price[SELECT: TIME.'Current Period']. But @DavidSmith pointed out in a different thread that you should prefer dynamic lookups. Then you need an assumptions module with a time period formatted line item (just two examples how you could name the line item).
Source Module.Price[LOOKUP: Assumptions Module.Price Period]
Source Module.Price[LOOKUP: Assumptions Module.Current Period]
Then you must assign a value to the assumptions line item with a function. For example the ones above could be: TIME.Current Period or PERIOD(CURRENTPERIODSTART()).