I assume you want to do this in a Visual Analytics Report, is that right? If so, I would move to the Visual Analytics board.
Please have a look at this post https://communities.sas.com/t5/SAS-Communities-Library/Calculating-First-and-Last-Days-of-the-Current-and-Future-Months/ta-p/307993 by @Renato_sas. He explains on how to calculate the dates your are after.
To save you some time, here is the formula to calculate n months from "now"
DateFromMDY(( ( ( Month('now - date'n) + ( 'n_months'p - 1 ) + 1200 ) Mod 12 ) + 1 ), 1, ( ( Year('now - date'n) + Trunc(( (Month('now - date'n) + ( 'n_months'p - 1 ) + 1200 ) / 12 )) ) -100 ))
Please note, this expression is using "now - date" (datepart of now) and a parameter named n_months. I used the parameter for testing purposes, -n to go n months back, +n to go n months forward.
Some other examples, First of next month
DateFromMDY(( ( Month('now - date'n) Mod 12 ) + 1 ), 1, ( Year('now - date'n) + Trunc(( Month('now - date'n) / 12 )) ))
Last day of current month, makes use of previous result
TreatAs(_Date_, ( TreatAs(_Number_, 'first_of_next_month'n) - 1 ))
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