Take a moment to go back in time when you were a child.

How did the passage of time feel in childhood compared to now?

If you’re like me, time seemed to move at a crawl in childhood compared to the speedy blur in adulthood.

Why did an hour feel like an eternity then and a year feel like an instant now?

Over this past decade, as I took my health and longevity more seriously, I began to wonder whether all of my efforts to objectively increase my healthy lifespan–through better diet and lifestyle habits–would be worth it if my subjective experience of time continues to compress as I aged.

What’s the point in adding years onto the tail end of my lifespan if those same years will feel like mere days?

Subjective vs objective experience of time

Our subjective experience of time does not match the objective pass of time. Early on, time felt much slower. But as we got older, time seem to speed up and fly by.

Let’s do some simple math and divide an average lifespan into three equal phases: Early, Middle, and Late.

For a person with a lifespan of 75 years, each phase will make up 25 years and look something like this.

Subjective Experience of Life: Time Factor of 1

If our subjective experience of time was the same throughout life, then the objective passage of time as well as our subjective experience of that time for each phase would be the same: 1/3 of the lifespan.

When our subjective experience is equal to the objective passage time, let’s call that a time factor of 1.

But we know that is not the case. So what would it look like if we experienced time differently throughout the life stages?

What if time passed by twice as fast?

If each successive phase felt like it passed by twice as fast, then the Early phase would feel twice as long as the Middle phase, and four times as long as the Late phase.

Subjective Experience of Life: Time Factor of 2

Now, if we experience time twice as fast as we age, have a time factor of 2. And even at a time factor of two, it’s clear to see that subjectively, the last phase of life that is 1/3 of our objective years will only feel like 1/7 of our life.

But for many of us, we have even more pronounced compression of our subjective experience time.

What if time passed by ten times as fast?

If each successive phase feels like it passes by ten times as fast as the previous phase, then our subjective experience of our life will look like this:

Subjective Experience of Life: Time Factor of 10

As you can see, a time factor of 10 will make the last 1/3 of your years feel as though they were only 1/111 of your life (less than 1%)!

How much life do we have left in any given year?

To find out. I built a calculator.

The results are both depressing and motivating.

I took the average lifespan of 79-year and broke it down into different stages.

For simplicity, I assumed that the first five years of life I have the longest subjective experience of time. And in my final five years, I will have my shortest subjective experience of time.

I take the middle year, at 40, and set it as the baseline year. Meaning, I compare all of the other years versus the year at age 40.

I’m in my 30’s with 40 just around the corner and time seem to pass a whole order of a magnitude faster than they did in my childhood.

So I set my time factor to 10–meaning the passage of time in my childhood felt 10x longer than they do now, and in my sunset years, time will feel 10x shorter than they do now.

With these assumptions, by age 40, I will have lived over 92.5% of my subjective lifespan!

Meaning, only 7.5% remain of my subjective lifespan!

If I objectively extended my lifespan by ten years, from 79 to 89 years, those extra ten years would only add an additional 0.39% to my subjective lifespan!

Even if I adjusted my time factor from 10x to only 5x, the results are not much better. At 5x, I will have lived over 85% of my subjective lifespan by age 40 and an extra 10 years would only add 1.34% to my subjective lifespan.

So how could we slow (or even reverse) the passage of time so that we could subjectively live longer?

How could we reverse the trend so our remaining life looked more like this? Where our sunset years feel longer and longer rather than shorter and shorter?

How much life do you have left?

Find out by playing with the calculator yourself using your own assumptions.

Just make a copy and change your assumptions using cells C4 and L4 to represent how the experience of time in childhood and the final years compare to your baseline experience at age 40, respectively.

(Note: this calculator is not the most user friendly. It does require you to be slightly comfortable working with a spreadsheet.)

Is this our default?

It doesn’t have to be. And it shouldn’t be.

By understanding what changed from childhood to adulthood, we could possibly slow or even reserve our subjective experience of time.

How can we completely flip the chart so that MOST of our remaining subjective lifespan is still yet to be lived?

Does it shift your focus from just trying to add years to your life to instead add more life to your years?

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