Hi,

To automate the creation of opportunities in your CRM each month based on a customer's order history from one year ago, you can set up a scheduled action in Odoo. This action will check for customers who ordered a product exactly one year ago and create a new opportunity for follow-up.

Go to Settings > Technical > Automation > Scheduled Actions.

Refer the following image to add the values to the field for your specification:

Hope it helps.