How to use variables for time comparison?

Jace Mclean has shown in the video published on Domo youtube channel that it's possible to use variables as date selector combined with time comparison (PoP vs YoY). This is exactly a business case that I have in my project.

My question - how this setup was created? What changes to the dataset/ETL were done? What beast modes are needed?

I've read documentation available on https://domohelp.domo.com/hc/en-us/articles/7903767835031-Variables-Overview, but I don't find this topic sufficiently explained for this particular use case.

Link to the video for the reference - https://www.youtube.com/watch?v=yzZEagCJ4Gc 24 min 42 sec is the start of the relevant part.