Birthdays and wedding anniversary dates I would like to know how to insert birthdays and wedding anniversary dates into contacts in my Android phone book.
Contrary to what another answer implies, you can't add any field you want when you tap the Add another field button in the stock contact editor. You can only add from a pre-defined list of fields. Unfortunately, the stock contact viewer and editor don't support custom fields. 

The good news is that you can add birthdays and anniversaries, though it's not immediately obvious how, because they're not independent fields, they're categories of the Events field. 

In the Add another field box, check Events and tap OK. You'll then have an Events field that works much like the Phone, Email, and Address fields: you can add multiple entries (by tapping the green plus sign), and for each one you can select the category from the adjacent drop-down list.

More good news is that you can add custom categories for events, just as you can for addresses and phone numbers: select Custom from the drop-down list, and enter your custom category. In this case you won't need to do that, though, because Birthday and Anniversary happen to be the two pre-defined event categories.