At a luncheon last winter, I sat next to a woman whose son, a high school junior, was about to go to Japan for four months. It was a special honor to be chosen for the program, and she was beaming with pride. She was overwhelmed a bit by the preparation for such a once-in-a-lifetime opportunity, but her attitude was mostly one of enthusiasm and silver linings: “Four months of freedom!” she gaily chirped. “I’ll miss him, but I’m actually looking forward to it.”

By coincidence, at this year’s luncheon (it’s an annual event) she and I were seated at the same table. This time, she told my tablemates about a recent “college night” at her son’s school, where she was hit by the sudden realization that he would soon be out of the house, not for four months, but forever. This time, overcome with emotion and wiping her eyes with her napkin, she sobbed, “I just can’t believe I’m almost done. My baby is almost out the door.”

Afterward, I thought about what she must’ve been feeling. But it was hard for me to truly grasp. With my own three children in first and third grades, I identify more with her disposition last year, when her boy was off on a grand, but temporary, adventure.

From the time you click “post” on the first scrunched-face picture of your newborn baby, friends, family and Facebookers begin telling you to enjoy these early years, because it all goes by so fast.

“Don’t blink,” they warn you. “It’ll be over before you know it.”

Intellectually, you know they’re right. After all, childhood is officially about 18 years, while adulthood — assuming we live to at least age 85 — is 67 years or more. I’m not great at math, but even I can calculate that we’re adults nearly four times longer than we’re kids.

Still, when you’re in the middle of it — night feedings, diaper changes, daycare payments, food aversions, temper tantrums, homework help, travel sports, social anxiety, preteen sullenness, teen rebellion and on and on — getting through childhood can feel so very, very long.

Some days, when I’ve put in a full day’s worth of work before even walking through the doors of my paying job, only to turn around and face after-care pick-up, dinner, homework assistance, piano practice overseeing, meltdown managing, showers, story time and kitchen clean-up when I get home, I feel like I’ve logged one calendar day but three emotional ones.

Right now, my life as a parent is firmly planted in the “days are long” half of that oft-heard saying.

The mom sitting next to me, crying about the joyous but bittersweet process of selecting colleges for her high school senior — she’s crossed over to the “but the years are short” part.

She’s remembering the times snuggling her son close while he slept, not the times he wailed until the wee hours and refused to sleep at all. She’s nostalgic for the goofy grin caused by lost teeth, not the stony face of a chastised teen who lost the car keys — again.

It’s one thing to know that her hard work is culminating: All the teaching, encouraging, hand-holding, prodding. All the tears spent, all the budgets blown. But it’s another thing to know that the young man who benefitted from all that hard work is embarking on an even grander adventure — one that, as time ticks on, will involve her less and less.

In the car on the way home from the luncheon, I remembered a moment recently when I was helping my 8-year-old son moisturize his dry skin with coconut oil. We were rushing, as usual, and I was surely thinking of other things when I noticed something that made my breath catch. Fine hairs had sprouted on his skinny legs, interrupting the smooth brown with soft, black hints of an adolescence to come.

Recalling the surprise of that moment, it dawned on me: Time is moving so much faster than I realize.

I felt for myself the pang that must be in her heart. And the tears fell — for her, and for me, and for the short years that are already, too soon behind us.

Tanika Davis is a former Baltimore Sun reporter who works in communications at Constellation. She and her husband have twin 8-year-old sons, a 6-year-old daughter, a perpetually messy house and rapidly appearing gray hairs. She also needs a nap. She can be reached at tanikawhite@gmail.com. Her column appears monthly.