Allowing for Null date fields

Currently a user must select a date from a date field.

What if we want to make it an optional field? A good example would be if we prompt for an optional Birth Date. Currently the system defaults to today's date. So, if the user does not want to enter his birth date, for obvious reasons, the system enters his birth date as today.

A year from now our user will be one year old!

We have functions that calculate our user's age. The way things are now there is no way for us to ignore dates where users decided to not enter their birth dates. So, users that did not want to supply this very personal information, is now treated as young children.

We must have a way to exclude/isolate those users who did not want to enter their birth dates. The only way to do so is to allow for a null date. That should also be the default when we prompt for a date, or maybe provide a parameter where you can set the default value of an initial/new date to either today's date or to NULL, or even better, any date you as the designer may want to choose for whatever reason.

Can someone please look into this.

Thanks.