AgeBreakdown app for iPhone and iPad
AgeBreakdown allows you to track the ages of anyone you want.
A persons age is broken down by year, month, and day allowing you to see how old anyone is in days, months or years.
You can impact information from your contacts, including birthdays (if available).
You can create yearly reminders for any one in your list. If the person is under 1 year of age, you will get reminders for every month up to a year.