It works better if you import the Facebook's birthday calendar in Google Calendar
If
Event from search starts
This Trigger fires a set number of minutes before the starting time of an event on your Calendar that contains a specific keyword or phrase in the event’s Title, Description, or Location. Ingredient will be based on the zone set in Google.
Then
Send a Pushover notification
This Action will generate a Pushover notification to your subscribed devices
Discover more time saving integrations for Pushover and Google Calendar