Time may fly when you’re having fun, but fun isn’t the only thing that can make time fly. Parents are already starting to ask where the summer went.

We see the notebooks and pencils start to replace the sunscreen and beach balls at the local drug store. The mailings from school start coming home. E-mails about fall carpools start flying back and forth. And before you know it, August is over.

While all of this planning is a necessary part of modern parenthood (especially for working moms and dads who can’t leave this stuff to the last minute), it also forces summer to end too quickly.

Rather than enjoy another four weeks of nice weather, more daylight hours, no homework and freedom from a strict schedule of school and extracurricular activities, we’re already gearing up for September.

And, sorry, it’s not simply out of necessity that we parents start hurling ourselves toward fall. It can also be very appealing.

Parenting can be tedious at times. And doing it with less structure — as we tend to over the summer — can make it worse.

The days after camp ends but before school starts can be a particularly trying time. Suddenly weeks of empty days stretch before us.

We can only arrange so many playdates or trips to the amusement park before we start staring out the window waiting for a school bus to show up.

Just think about life before children. (I know; it’s hard to remember sometimes.) For middle-class parents, their existence prior to having kids revolved around work and friends.

Even if your job wasn’t the most scintillating, you could get through it and meet your friends for drinks afterward.

And during the workday, you had at least a chance to keep busy enough that time went by pretty fast. Psychologist Mihaly Csikszentmihalyi calls this “flow,” that blissful state where you’re so engrossed in the task at hand that you don’t notice time passing.

It’s near impossible to stay in a state of “flow” when you’re caring for a small child, as Jennifer Senior observes in her book “All Joy and No Fun” — at least in part because your attention is constantly being refocused as the child changes moods and activities.

You’re in the middle of your pretend tea party that’s taken 10 minutes to set up when suddenly she wants to go find her left slipper. Or she has to go to the bathroom.

Or you can see that she has to go to the bathroom but she denies it. So you spend the next three minutes arguing about it — until the doorbell rings and she starts demanding a snack while you’re negotiating with the electrician.

In so many ways, it’s more worthwhile to spend the time with the child than to enter numbers on a spreadsheet, but there comes a moment in the day of every mother where she longs for the spreadsheet.

A friend of mine, a married full-time stay-at-home mother of three, once described to me the change in her life after she left work as a magazine editor. “You know how you have lists, Naomi?”

I laughed. Fresh out of college, we used to keep neat pages of tasks, personal and professional, that had to be accomplished each day, or each week.

“Well,” she continued, “I start each day with a list. And nothing ever gets crossed off.”

Gearing up for the fall is a way we can start crossing things off of our lists again, start trying to achieve flow again.

Problem is, that’s not what childhood is about.

Childhood is about slowing time down. Kids are learning about the world. They’re supposed to be taking their time appreciating the color and beauty of nature, trying to understand how things work, how people work.

Our lives necessarily require a certain amount of efficiency — we can’t just ignore deadlines and paychecks and household repairs and shopping lists — but there’s something to be said for slowing our pace in these next few weeks.

Summer isn’t endless, after all.

Naomi Schaefer Riley is a senior fellow at the Independent Women’s Forum.