By default BirthdayBot posts congrats on Mondays for the users whose bday falls for the weekend, however, you can adjust the time and day for congrats in the settings.
Let's find BirthdayBot in the Slack Apps section, open its Home tab, and click the Settings button on the bottom of the layout.
Once a new window pops up, select the Workspace settings in a drop-down (available for BirthdayBot admins only),
and specify the time when you want the bot to do the birthday hoopla.
Still have questions about BirthdayBot?
Don't hesitate to contact us.