easiest way is to convert them to days and subtract. if they are <=31 days apart, then true. the problem is question is a bit ambigious as what exactly a month apart means as different months have different days.

The question has no answer until more information is provided. What is a month apart? Is it 31 days, 30 days, 29 days, 28 days? Is it the day of month "number" for the later date is less than the day of month "number" for the earlier date? And other undefined conditions. All conditions must be known before a valid method can be defined and verified as valid.