This really depends on what your needs are. You can restrict the display of any date value to show only month or month and year, but you will still be storing the full date. I would recommend this. However, if you want to just store the month or mth/year you would need to use a text field to do it. If you want to store month number and year you could do it in either a text ro numberfield. For numeric fields I'd use a Long integer field and set the format to: