There are various instance when we do date calculation on date / unix datetime fields.Following are some example as how to use inbuilt functions of mysql which will reduce doing calculation in PHP, I hope it will help someone:
SELECT DATE_ADD( '2008-01-02', INTERVAL 1 MONTH )
OR if you want to add date to current day than you can use like this:
Select DATE_ADD(now(), INTERVAL 1 MONTH);
OR if you want to add a month while querying on your table fieldname than just replace now() with your field name like below:
Select DATE_ADD(fieldName, INTERVAL 1 MONTH);
If you are storing date as unix timestamp than than you can do like this: