How to make a monthly calendar?

I am working with deadlines -normally two weeks, sometimes more. Therefore I want two monthly calendars side by side for easy finding the end date of the wished deadline.

I have found some ready to use monthly calendars which work fine. But they always start at the actual month. I want one with the actual and one with the next month.

The monthly calendar I found and use does not show formulas or some I could see. I don't know how they make a calendar my own, too. Even I could not find a tutorial for it.

Is there a tutorial how to make a monthly calendar?

Thank you!