We have the below requirement to calculate the previous 12 Months sales data ?

For example if we provide 2015-01-01(date) as a variable (Single input variable) client would like to view the data from 2014-01-01 to 2015-01-01 as 12 months data

How can I calculate the same under Calculation view.

how can i write expression for single input variable.

for work around i have created range variable but client is asking for single input variable for month and it retrieves 12 months data.