Are you looking for a real calendar or would you like to have a date time picker for year and month only?
First: I think you could use the calendar widget from the app store https://appstore.home.mendix.com/link/app/107954/ . As far as I know you can customize with built-in features so that selecting year and month is possible.
Second: I don’t think that this is available as a widget, if you want you could just provide an enum with reasonable year entries and parse the user selection from the caption to the desired date time format?