It's a sad fact that those can get in the way of other, equally important milestones.
Like getting your ears pierced (age 5.5),
Being on the cover of a book (photo of Ellie around 8 months old)
(Couldn't find my own picture, but hey, you can click the photo and order the book!),
Watching the Cubs for the first time (4 months),
Visiting the beach for the first time (4.5 months),
Or getting a baby sister (4.5 years).
Those things matter to varying degrees, but they will probably prove more memorable for Ellie than the ages at which she hit traditional milestones.