Janet's Law — How to Counter Time Feeling Shorter as You Age
It Started With a Senior’s Remark
Suddenly, it’s the end of the year again.
You know the feeling?
When I was a kid, a summer vacation felt eternal — day one to the last day stretched out forever. Now, a whole year flips by like turning a page.
One senior at the office once put that feeling into words for me:
“As you get older, a year flies by — you age as naturally as breathing.”
He said it casually at a company event, and it stuck with me. I’m 27, so I don’t fully feel it yet. Still, recent years really do pass at a different speed from the years I remember as a kid.
This sensation actually has a name: Janet’s Law.
What Janet’s Law Says
It’s a psychological observation proposed by the 19th-century French philosopher Paul Janet. In one line:
As the ratio of one year to your total life shrinks, subjective time feels shorter.
The numbers make it intuitive.
| Age | Ratio of 1 year | Perception |
|---|---|---|
| 5 | 1/5 of life | A year feels very long |
| 27 | 1/27 of life | A year passes fairly quickly |
| 50 | 1/50 of life | A year flies by |
A year for a five-year-old and a year for someone at fifty are literally different lengths to the brain.
The ratio decline itself is unavoidable. Time passes equally, regardless of how we feel about it.
But here’s the part with hope.
Janet’s Law has a second dimension: when new experiences decrease, brain activity drops, and time feels shorter. And this part — you get to decide.
Stop Your Brain From Defaulting to “Known Patterns”
When new experiences thin out, the brain processes everyday life as “the usual.” There’s no need to record it specifically.
So at year’s end, you look back and ask: what did I even do this year? That feeling of “I did nothing, yet the year is over.”
Flip that around: if you deliberately keep slotting “new” into your life, you can stretch subjective time.
Here’s what I personally try.
- Touching unfamiliar tech outside of work — My day job runs on .NET / SQL Server, but in personal projects I dive into Flutter and Astro — completely new textures. Building an app in 3 weeks with AI-driven development gave me a tangible “the brain is actually moving” feeling.
- Using certifications as a forced learning loop — Fundamental IT Engineer → Applied IT Engineer → LPIC → OSS-DB → Python certifications. Honestly, half the motivation is “I want external pressure to study.” Exam prep doesn’t review what I know; it drags me systematically into what I don’t.
- Making output a habit — Articles on Qiita, reflections on this blog. Pure input keeps the brain quiet. It’s the moment of putting things into words that surprises me with new angles.
- Never letting personal development stop — YumeHashi / Defrago / this homepage. The act of building keeps quietly delivering new problems to my doorstep.
None of this is flashy. But lately I’ve come to think that stacking small, plain things is the only real resistance against time slipping by.
Time Is the Most Valuable Asset You Own
My senior’s words made me rethink time from the ground up. I landed on this: time is more valuable than cars, houses, or money.
The reasoning is simple.
- You can’t recover it — Lost money can be re-earned. Past time? Nobody hands it back.
- You can’t control it — No one knows when it ends, not you, not anyone else.
- It’s given equally — 24 hours a day. This, at least, everyone has.
An asset you can’t recover, can’t control, and yet receive in equal portion. That’s exactly why I want to pour it into what I genuinely care about.
What I care about, written in my profile’s “Dream” section, is “building a society where people can hold and speak their dreams.” It’s huge, and not something one person can finish.
Even so, I trust the 1.01 rule in my motto and choose to move 1% forward today.
”Be Present” — But, Specifically
“Live in the present.”
It’s a beautiful sentence. And it’s true.
The problem is, by tomorrow morning I’ll have forgotten it.
So I’ve broken “be present” down one layer.
- Write code or read tech articles every single day — Never let a day go to zero.
- Always put what I learned into words — Stop the brain from drifting into “known pattern” mode.
- Try something unfamiliar at least once a year — Force-feed the brain a “first time.”
- Revisit my short / mid / long-term goals on a schedule — A compass so the days don’t just drift by.
Time isn’t going to stop. But I’d rather keep struggling against the current than be carried by it. That’s the conclusion my senior’s single sentence eventually led me to.
If you’ve ever closed a year and thought, “that went strangely fast,” try slipping just one non-usual thing into your day today. Whether it sticks as a memory six months from now will be the most honest answer you can get.
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