The report has all sorts of tidbits for interaction designers about date formats, error trapping, leading zeros, and more.

One thing the study doesn’t discuss is when not to use dates.

I recently recommended, in an online customer-registration form, dropping the request for the customer’s complete birthday. On the site, the date will be used to compare the customer’s data to a comparable sample of the same age. The site will tell the user whether they’re below or above average.

The point behind my recommendation is this: you can accomplish that with reasonable accuracy with only the month and year, or perhaps with only the year.

Unless your business or the application really needs to know a user’s exact date of birth, collecting that information online means you’re setting up your company, needlessly, by making its data a juicier target for hackers and identity thieves.