Relational Database Persistent Data

I’m building a relational database for a small high school lab for the purposes of stock controlling (and recording where everything is).

I am stuck (wondering) on how to keep previous years data while still being able to update the data as it is seen in the tables, I added a date field to record when the data changes.

What I want to do is to record the changes in stock from year to year and if the stock is not updated, the last record of the stock.