I have a fairly large family and often have trouble keeping track of birthdays, anniversaries, and the like. I've also started keeping track of my family's genealogy via a web-based package, so the solution seemed obvious: add the component I needed so the software I was already using. The result is called tngCalendar. The calendar is a simple monthly view with birthdays, wedding anniversaries, and dates of death overlaid.
tngCalendar operates in conjunction with the TNG package, but can (and should) be installed separately. Simply download the package, and uncompress in a temporary directory. Edit the php file according to the directions contained inside, and copy the pieces into place.
Note that tngCalendar may circumvent your security setup by "giving away" birth and marriage dates relevent to living persons. However, since the exact year of a person's birth or marriage is not shown on the calendar (it only shows anniversaries, the year is only used for day-of-the-week layout), this is usually an acceptable risk.
tngCalendar was meant to operate with the latest version of TNG (v5 as of this writing), but may work with earlier versions. It should be compatable with any version of PHP.