MySQL has a PERIOD_ADD() function that allows you to add a number of months to a given period. It returns a value in the format YYYYMM.
This article provides examples to demonstrate how it works.
When using MySQL, you can use the MAKEDATE() function to return a date from the year and day-of-year parts.
In other words, you provide two arguments; one being the year, and the other being the day-of-year. The MAKEDATE() function will then return the date value based on those two arguments.