Show Birthdays and other dates in contacts on calendar

Currently, the calendar is independent of the contacts database. It would be nice if there were checkboxes for each group tag, to manage the display of date events in the contacts database.

Example, on a specific date:
~~~
John Doe
Birthday 7/4/1976
~~~
or
~~~
Call John Doe (123)456-7890
Re: See if his budget was approved