Dates to iCal is an app that syncs birthdays and anniversaries in your Address Book to iCal, adding them as alarmed events to a separate calendar.
You can also add other customized Address Book date items to iCal and even add birthdays for people for whom you don’t have a separate Address Book card.
The interface windows demonstrates most of the app’s options:
You can set the kind of alarm that iCal will provide (email works best for me) and choose the advanced notice you need.
After importing the events are fully-editable so that you can customize them or add notes.
Dates to iCal is donationware and is available from the developer’s web site 
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How is this different than selecting “Show birthdays calendar” in iCal preferences ?
With this preference, all the birthdays entered in Address Book show up automatically in iCal. What am I missing here ?
Hi Vincent,
The main difference is that with iCal’s built-in birthday calendar you cannot add alarms… or sync anniversaries & custom dates… or list someone’s birthday without having to making a card in Address Book.
[...] *Using iCal to send a calendar event via Mail to other iCal users. *(ZappTek provides hacks ) to help other email clients send iCal notifications.) There are several third party Applescripts and programs that expand on the built in features. * iCal Events Widget * [Syncing birthdays and other events with Address Book](http://www.hawkwings.net/2006/03/14/dates-to-ical-syncing-birthdays-anniversaries/( [...]
[...] Dates to iCal is an app that syncs birthdays and anniversaries in your Address Book to iCal, adding them as alarmed events to a separate calendar. [...]