Power Query Calendar Table

I have a calendar table that I have been using for a while and I need an adjustment and can use some help.

What I would like to do is add one month to the date. For example, if I select January form the month slicer and 2022 from the year slicer, this will represent December 2021.
We pay invoices within 30 days of receipt, so in January 2022 we are looking at December 2021 expenses.

Any help is appreciated.

will be better if you attach example excel file with what you have AND what you want to achieve
with detailed description

@sandy666, Thank you, I should have mocked up an example. I was able to figure it out on my own. If I add a custom column and use the following formula:

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I was able to achieve what I need.

Thank you again for taking the time to answer my question.

Joe

that's good you solved the problem
have a nice day