How do I calculate the difference between the newest value and the oldest value?

lindelwebhebhe , do need a row-wise difference or month wise. In case you need month-wise you can use time intelligence

I would prefer to create a date column or use the Rank way, example of the week shared

date =date(left([cycle_num],4),right([cycle_num],2),1)

Example with a date table

MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD('Date'[Date]))
last MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(dateadd('Date'[Date],-1,MONTH)))
last month Sales = CALCULATE(SUM(Sales[Sales Amount]),previousmonth('Date'[Date]))
Next month value =  CALCULATE(sum('table'[total hours value]),nextmonth('Date'[Date]))
previous month value =  CALCULATE(sum('table'[total hours value]),previousmonth('Date'[Date]))

diff = [MTD Sales]-[last MTD Sales]
diff % = divide([MTD Sales]-[last MTD Sales],[last MTD Sales])

Power BI — YTD
https://medium.com/@amitchandak.1978/power-bi-ytd-questions-time-intelligence-1-5-e3174b39f38a
Power BI — QTD
https://medium.com/@amitchandak.1978/power-bi-qtd-questions-time-intelligence-2-5-d842063da839
Power BI — MTD
https://medium.com/@amitchandak.1978/power-bi-mtd-questions-time-intelligence-3-5-64b0b4a4090e
Power BI — WTD
https://medium.com/@amitchandak.1978/power-bi-wtd-questions-time-intelligence-4-5-98c30fab69d3
https://community.powerbi.com/t5/Community-Blog/Week-Is-Not-So-Weak-WTD-Last-WTD-and-This-Week-vs-Last-Week/ba-p/1051123

To get the best of the time intelligence function. Make sure you have a date calendar and it has been marked as the date in model view. Also, join it with the date column of your fact/s. Refer :
https://radacad.com/creating-calendar-table-in-power-bi-using-dax-functions
https://www.archerpoint.com/blog/Posts/creating-date-table-power-bi
https://www.sqlbi.com/articles/creating-a-simple-date-table-in-dax/

See if my webinar on Time Intelligence can help: https://community.powerbi.com/t5/Webinars-and-Video-Gallery/PowerBI-Time-Intelligence-Calendar-WTD-YTD-LYTD-Week-Over-Week/m-p/1051626#M184


Appreciate your Kudos.