Hi @milovan9926 - welcome to the community! I recommend you take a look at this article that shows you how to setup a Flow on a “Date Triggered” event.
It requires a bit of setup of custom properties, and you will have to upload the list of people with their “birthday dates” into Klaviyo. But once the dates are in your users’ profile, you can then automatically send an email on that given date (or X days/weeks before that date).
When you’re uploading your dates into Klaviyo, one thing that is often tricky is making sure the “date” is in a format that Klaviyo accepts. Here’s more info on that:
As a bonus, instead of uploading dates into Klaviyo manually, you can also create a Flow to automate this in the future by setting up a Flow that adds the “date” to Klaviyo - you’ll have to set some Flow Filters to determine which orders are considered “Birthday Purchases” - but if you can, then you can follow this guide to update a Profile with that date:
Hope this helps!