We humans measure our threescore and 10 in disparate ways.

I had a short-timer's calendar in the U.S. Army, marking off my final 365 days of service. Each morning I'd dutifully scratch off another day.

The count of Monte Cristo painstakingly marked the passage of time on the granite walls of his prison cell.

For many, time measurement is simply the annual accrual of birthdays. Like logs at the bottom of a sluice, they pile up.

For others, it's the inexorable drip-drip-drip of TGIFs. For some Europeans, it's the repetitive ringing of church bells. For many, time is diurnal and circadian — based upon sunrises and sunsets.

For Henry Wadsworth Longfellow, it was the cyclic rise and fall of the sea: "The tide rises, the tide falls / The twilight darkens, the curlew calls / Along the sea-sands damp and brown / The traveler hastens toward the town / And the tide rises, the tide falls."

Perhaps we delineate our lives by sports moments or memorable seasons. Remember 49er quarterback Joe Montana's 28-point comeback victory over New Orleans in 1980? (Ah, 34 years ago.) Or L.A. Dodger Kirk Gibson's pinch-hit, walk-off home run to beat Oakland in Game 1 of the 1988 World Series? (Twenty-six seasons ago.)

The wise King Solomon measured life by different sorts of seasons. He wrote: "To every thing there is a season, and a time to every purpose under heaven."

We each tabulate our seconds, minutes, hours, days, weeks, months, years and decades differently, but tabulate them we do. And we're not alone. I'd wager some celestial actuary stands at the eternal gates — ledger in hand — adding up columns of figures and making notes. Perhaps there's an ETA printed alongside each name.

For me a means for assessing the passage of time is the tried and true "Significant Female in my Household Turning 40" method.

I realize that sounds bizarre, so permit me to explain. In my case it has to do with four of the most venerated females in my life reaching a certain numerical milestone. Try this: "Where was I when (insert the appropriate venerated name) turned 40?"

My grandmother turned 40 on Wednesday, Jan. 16, 1946. I was there to be sure, though I must confess, I have no recollection of the occasion. For me, it was a washout. I was three days shy of turning a year old.

My mother's odometer rolled over to the "big four-oh" on Tuesday, March 31, 1964. Mom had always seemed so young to me, and it was almost unthinkable that she could be entering the dreaded black hole of human habitation.

I was 19 and in my fifth week of basic training at Fort Ord, near Monterey. I called Mom that evening from a public telephone in the dayroom of my barracks to wish her a happy 40th. With $5 in dimes and quarters spread before me, I seriously didn't know what to expect from her: black crape paper and tears, or streamers and laughter?

Fortunately, it was the latter. She was in good spirits (just as she was a few weeks ago when she turned 90!). What could be better? Dad had taken her to dinner, and she'd just received a call from her soldier-son.

I was 46 when my wife, Hedy, turned 40 on Sunday, Jan. 27, 1991. We celebrated at an after-church brunch at her favorite Newport bistro.

I was 66 when my eldest daughter, Jenn, turned 40 on Friday, July 22, 2011. I confess, it felt a bit like I'd been punched in the solar plexus: "My baby is 40!"

Is there the slightest chance I'll be around when my oldest granddaughter turns 40 in 2041? Nah. So it would appear that my "Significant Female in the Household Turns 40" ceremonials are winding down. But I look forward with anticipation to my two younger daughters turning 40 in 2015 and 2018, respectively.

Admittedly, significant 40th female birthdays can be problematic for guys marking time. I'd suggest a smarter approach: Move to an alpine valley and listen for church bells.

JIM CARNETT, who lives in Costa Mesa, worked for Orange Coast College for 37 years.