Because it takes you a month for another shopping, you don’t want to make a purchase some product only to find out you missed out some items. So make those calendars into a shopping list. Translate those menus into a list of ingredients and eventually a shopping list. To make it more convenient, group your list according to the department, it will make your shopping easier.
Improvise. You will likely experiencing some flaw in your carefully laid out plan, so when it happenstry to improvise. Make modifications to your menu, use whatever you have in store. The error in your planning will go away once you get more experience in doing monthly shopping.