There is no such option or parameter I am afraid
But, there is a possible workaround, if you think about it
Create on placeholder user and in his AcyMailing user profile, set his birthday field to the specific date
After that, use create an Automation and set "Trigger based on user action" -> "On user birthday"
Under the condition, select "AcyMailing field" and check if email field value is exactly that placeholder email address
Under Actions, add email to the queue
Under the Action targets, select "Execute the action on all subscribers and set required filters
That could work
Can you please try it?
