create an entity add a date attribute. create a microflow that will populate the table with prefilled dates.use a loop to create date objects for each month and add them to the table. and call the microflow and you can do this in a startup microflow or by adding a button to a page that calls the microflow when clicked.This approach should create a table with pre-filled dates for each month of the current year. You can modify the microflow to adjust the year or the number of months if needed.
You can do a lot with dates in microflow expressions. Check out the docs for help https://docs.mendix.com/refguide/expressions/#11-date-creation