We store all your historical ranking data when you track keyword rankings on the Authoritas platform. To see how your rankings have changed over time, you simply need to:
1) Go to the Ranking Tracking module and click on the '+' icon:
2) Then select 'Dates' (pink arrow) and click on whatever dates you want to compare (yellow arrow) and then click on Apply (green arrow):
3) You'll then see the following view, which compares the ranks on the selected dates side by side:
You can also export a .csv or .xls file by selecting "Ranking History' report from the 'Export' menu above the chart widgets.
We also have a lovely Google Data Studio template that tracks your keyword rankings and SEO Visibility share of search% over time (check whether this is enabled on your package).