Narrative reporting EPM add drop down date column

The user wants a drop-down option to select a date in the MMM-YYYY format in Narrative reporting- EPM.

I added a "Notes" column to enter the date, but since it is free text, we cannot restrict it to a specific format. The user would like a drop-down selection to ensure all users input the date in a consistent format.

Could you please provide a solution on how to implement this functionality?