How to use if elif and else in python to perform an action to create a new json file every month, on the first day of each month?

I have a python script that stores a row of data every minute for every day and every month of the year. However, because there is so much data stored per day, the json file ends up with 518,400 lines of data per year, with a size of 67MB.

I need to make a script that executes an action to create a new json file every first day of each month of the year, therefore, it will not accumulate all the data of the year in just one file, which will result in a json file for January, February , March ... December.

The first idea I had is to use if elif and else in python, but I don't know how to do that.

Does anyone know how I can do this?

This is the format of my json file: i.imgur.com/jDzhWRI.png