While you can send your customers a message on their birthday from the 'Client Birthdays' section, you can configure your Diarize Me account to send your clients a birthday message automatically.
To enable this, click on 'Settings' and then on 'Client Notifications':
Scroll down to the section that is titled 'Client Birthday Messages' and click on the 'Edit' button.
From this screen, you can enable the automatic birthday message, set the time that your birthday messages will go out, and configure the message that gets sent to your client.
The system will find clients that have birthdays each day at the time you specify and send them the message you have set.