I previously shared how to create a “Today” column in SharePoint that would always be up-to-date even if list items weren’t modified. These were no-code solutions that utilized either SharePoint Designer or Microsoft Flow. You can, however, use Today’s date/time to create views and calculated columns without workflow or script or the need to create another column.
DateKeys are essential for relative time measures. In “manage relationships” you tie the ‘DateKey'[Date] to a date field in each of your data sources. Giles Walker shared an excellent solution for a robust DateKey that includes measurements and calculations you’re sure to find useful. Here’s that same solution I’ve modified and expanded to be as useful as possible.