Go to Settings > Calendar > General.
Go to the tab Attentions.
(Un)check a box to add or delete an attention.
Click on Save.
Go to Settings > Calendar > Custom attentions.
Click Add attention and fill in a name for the event.
Select a general or custom event for which an attention should be generated and the lactation.
Fill in the name of the attention and when it should be generated.
Click Ok to save the new calendar attention.
Go to Settings > Calendar > Custom events.
Click Add and fill in a name for the event.
Click Ok.