Calculating Spend Last Month Using a different calendar

[leekarensl]

Hi there, my client works using advertising flight months rather than calendar month. I have created a table called Flight month which states the dates that is within their definition of a month. For example for April, the dates will be 29th March to 27 April. I now want to create a measure to calculate the sum of spend for the previous month. I have tried to use the previousmonth function but it is not working. The flight month has a relationship to the main data table through date column in flight month and calendar_date column in test table.  

Thanks in advance for any help. The file can be found here 

[Walt1010]

I think the method described in this post could be helpful for your problem: (2) Custom Fiscal Calendar with Pre-Defined Date Range... - Microsoft Fabric Community

[johnt75 · Accepted solution]

I think you can use the principles described in https://www.sqlbi.com/articles/comparing-different-school-terms-in-power-bi/ 

[leekarensl]

Thank you so much once again! This works perfectly!