Few things mark the passing of time for me more readily than the start of a new school year.

For adults change comes slowly; an extra belt notch here, a few more gray hairs there.

But for kids change is often both explosive and exponential; something I seem to notice more as summer ends and the school doors open.

Is this the same kid I saw in May?

It also seems that as we age we become either less willing or less able to express pure joy and excitement.

That's not a problem for elementary school kids getting off the bus or walking the halls for the first time in months. There's new classrooms to explore and new schedules to master. There are kids to say "Hi" to who haven't been seen in months.

It's not Christmas, but it's got that kind of feel.

My teenage daughters are now well past any giddy phase. They are far too cool to get excited over something as mundane as a new school year and they roll their eyes if their father suggests otherwise.

But there are still glimmers of excitement they can't hide; like modeling their first day outfits around the house or texting their anticipation to friends.

It's a far cry from 11-years ago, when Dad walked his nervous oldest daughter up to the bus stop. While Dad was clicking away on the camera, she took her first tentative steps into the belly of the giant yellow beast.

It's hard not to think back on those days as the school bells ring in a new year, and it's hard not to have some mixed feelings too.

 You can be proud of what they are and still miss what they were.