In MySQL date intervals, is 1 MONTH the same as 30 DAY? Is 1 QUARTER the same as 3 MONTH? And so on?

Question

I am trying to write a PHP script that will process recurring payments every month, quarter, year, etc. This script will run as a nightly Cron job.

I don't want to run into a situation where somebody subscribes, say, on the 15th of a January, and then gets billed again on the 1st of February.

Is that what would happen if I checked the last payment against INTERVAL 1 MONTH? Or would it be the same as INTERVAL 30 DAY, and only process the payment again on the 15th of February, which is what I want?

Answer 1

Accroding to MYSQL

If you add MONTH, YEAR_MONTH, or YEAR and the resulting date has a day that is larger than the maximum day for the new month, the day is adjusted to the maximum days in the new month:

mysql> SELECT DATE_ADD('2009-01-30', INTERVAL 1 MONTH); -> '2009-02-28' Date arithmetic operations require complete dates and do not work with incomplete dates such as '2006-07-00' or badly malformed dates:

Thus if you use the 1 month built in function you do not have to worry when the last day of the month is. MYSQL does all the work for you.