I am trying to create a report which use current month as period. I was wondering if there is a way to pick month convert it number for calculation. Does anyone tried it before?
I am unsure on answering your question directly, but maybe you can do a different calculation using the {period_count} functionality in custom mode found on this page?
Aside from the {PERIOD_DAYS}, there is a hidden gem where you can use case statements in Custom formulas. Below is an example where I need to get sales for the last weekday using a SQL function to drive the logic:
^CASE WHEN DATENAME(weekday,GETDATE()) = ‘Monday’ THEN {a} ELSE {b} END
{a} = sales for yesterday - 2
{b} = sales for yesterday
You could do something similar if there are no better methods.