[AI Manga] Episode 26: That "daily difference" might not be the same every day? | The "Don't expect a personality from an alarm clock" problem in the world of watches

監修者 Commit Ginza
Kenji
Appraiser, I have a problem.
Yesterday, my watch was +5 seconds fast.
But today, it was -8 seconds slow.

Doesn't this watch have a personality?
Like, yesterday it was positive, and today it's feeling down due to low atmospheric pressure.
Appraiser
First, I don't recall installing a weather app on your watch.

The daily rate of a mechanical watch doesn't necessarily stay the same every day.
It can change daily depending on its position, winding amount, temperature, how it's used, and how it's measured.

In other words, it's not that the watch has become moody, but rather that its working conditions vary daily.
Kenji
Working conditions...
So, the second hand needs a shift schedule, then.

"Monday: on the wrist, Tuesday: on the desk, Wednesday: midnight shift by the bedside," something like that.
Appraiser
(If we start managing the second hand's labor, the minute hand might start asking for paid leave...)

① "Daily rate" is not a personality test for your watch

Appraiser
The daily rate, in simple terms, is a guide to how much time it gains or loses in a day.

For example, "+5 seconds daily rate" means it gained about 5 seconds in a day.
"-8 seconds daily rate" means it lost about 8 seconds in a day.

However, what's important here is that the daily rate is not always the exact same number every day.
Kenji
I see.
I thought the daily rate was like a report card for the watch.

Something that would say, "Yesterday +5 seconds, today -8 seconds. Lacks stability."
Appraiser
Looking at it like a teacher's comment section is a bit too harsh.

A watch's accuracy changes depending on how it's placed and used.
To conclude that "this watch is no good" based on a single day's number is like judging someone's entire life based on one instance of oversleeping.
Kenji
Judging a life based on one instance of oversleeping...
That's harsh.

If you only looked at me on Monday mornings, I'd be a bed accessory, not a working adult.
Basics of interpreting daily rate
  • Daily rate is an estimate of daily deviation: A gain is often expressed as plus, a loss as minus.
  • Not always the same number every day: Varies with position, winding amount, temperature, usage, and measurement method.
  • Don't judge by a single day: It's more realistic to look at trends over several days.
  • Large changes are a separate issue: Consider inspection if there's a sudden, significant deviation.
  • Material for checking condition of used watches: Daily rate is important information for understanding its current operation.

② Even if it was +5 seconds yesterday and -8 seconds today, it doesn't mean the watch is rebelling

Kenji
But it gains time yesterday and loses it today, that's quite concerning.

It feels like the watch is saying, "I'm not the same as yesterday."
Is it in its rebellious phase?
Appraiser
It's not the watch's rebellious phase.

The daily rate can change depending on when it was measured and how it was positioned.
The conditions are different between a day it was worn on your wrist and moving, and a day it was left on a desk.

Even for a person, wouldn't their expression be different on a holiday compared to a Monday morning?
Kenji
Indeed.
On Sunday, I'm as soft as pudding, but on Monday, I'm dry toast.

Even with butter, I still don't want to go to work.
Appraiser
(Kenji's condition at the start of the week might need an HR meeting more than his watch...)
Main reasons daily rate changes from day to day
  • Positional error: Accuracy can change depending on the orientation the watch is placed in.
  • Winding amount: Stability of movement can vary with the tension of the mainspring.
  • Usage time: Conditions differ between days with long wearing times and short ones.
  • Temperature: Can be affected by environmental factors like heat or cold.
  • Measurement method: Numbers can fluctuate depending on the time of day and the reference point used for measurement.

③ Positional error is like the watch's version of "condition changing based on sleeping posture"

Kenji
Positional error? Watches have posture?

So, should I tell my watch on the desk,
"Straighten your back"?
Appraiser
Even if you warn a watch about slouching, the second hand won't improve its posture.

Positional error is when the accuracy changes depending on the orientation the watch is placed in.
Placing it dial up, on its side, or crown up.
These different placements can slightly alter the internal movement.

For humans, it's like how sleeping on your back, side, or in a weird position affects your neck the next morning.
Kenji
I understand.
When I wake up from a weird sleeping position, my neck hurts as if "yesterday's meeting isn't over yet."

So, a watch's mood also changes the next morning depending on its sleeping position.
What happens due to positional error
  • Daily rate changes with placement: There can be different tendencies for dial up, dial down, sideways, etc.
  • Conditions differ from when worn on the wrist: Movement changes between storage and use.
  • Appears as numerical fluctuations: The difference between yesterday and today can sometimes be due to positional error.
  • Individual differences exist: Even within the same model number, tendencies can vary based on condition and adjustment.
  • Recording storage position helps visibility: Noting the orientation it was placed in makes it easier to judge.

④ Winding amount is like the watch's "breakfast"

Kenji
Is the winding amount really that important?

Is my watch going to work without breakfast, perhaps?
Appraiser
That analogy is quite close.

A mechanical watch is powered by a mainspring.
There can be a difference in the stability of its movement between when it's fully wound and when it's running low.

Even for humans, wouldn't the sharpness of your remarks be different between a day you had breakfast and a day you attended a meeting on an empty stomach?
Kenji
Yes, they would.
During an empty-stomach meeting, I'd be reading flyers for lunch boxes before the actual documents.

So, when a watch is "hungry," its second hand also looks dazed.
Appraiser
The second hand doesn't have eyes, but I understand what you mean.

If it's a hand-wound watch, wind it appropriately.
If it's an automatic, the winding might be insufficient if the time spent wearing and moving it is short.
When checking the daily rate, you'll want to be mindful of how fully wound it is.
Key points to consider with winding amount
  • Immediately after winding?: Check if it's sufficiently wound.
  • Not just before stopping?: Stability can be poor when power reserve is low.
  • Is wearing time sufficient?: Automatic watches are prone to insufficient winding if wrist movement is minimal.
  • Standardize measurement conditions: If conditions vary each time, comparing daily rates becomes difficult.
  • Don't panic just by the numbers: If winding is insufficient, first normalize conditions and re-check.

⑤ A day worn on the wrist is not the same job as a day left on the desk

Kenji
So, the daily rate can change depending on whether I wear it on my wrist or leave it on my desk?

Is it as different as a watch having a day of outside sales versus a day of working from home?
Appraiser
Quite similar.

When worn on the wrist, the watch's position constantly changes.
If it's an automatic, the winding also progresses with arm movements.

On the other hand, if it's left on a desk, its position is fixed, and winding doesn't progress easily.
Therefore, even with the same watch, the daily rate can change if its daily routine is different.
Kenji
So watches were also affected by work style reforms.

Wrist work, desk work, drawer standby.
Soon the second hand might say, "I'm working remotely today."
Examples of daily rate changing with usage conditions
  • Day worn for a long time: Position changes, winding progresses easily.
  • Day with little movement: Automatic watches are prone to insufficient winding.
  • Day left on a desk: Daily rate tends to be consistent in a fixed position.
  • Day stored in a different place: Temperature and placement might change.
  • Day measured at a different time: Difficult to compare unless viewed in 24-hour increments.

⑥ Temperature is like "summer ice cream and winter toothpaste" for a watch

Kenji
It changes with temperature too?

A watch seems like a block of metal, so I'd think it's strong against heat and cold.
It definitely won't get summer fatigue before I do.
Appraiser
Because a watch is a precision instrument, it's not entirely unaffected by temperature.

Extreme high or low temperatures can affect the condition of its components, lubricants, and how it moves.
Even within normal daily use, conditions differ between summer and winter, indoors and outdoors.

It's like summer ice cream and winter toothpaste.
The contents are the same, but their behavior changes with the environment.
Kenji
Summer ice cream melts quickly, doesn't it?
And winter toothpaste acts like it's saying, "I'm not coming out" in the morning.

So, watches also change their attitude a bit depending on the environment.
Things to be careful about with temperature
  • Do not leave in high-temperature places: Avoid car interiors and direct sunlight.
  • Low-temperature environments also change conditions: Movement can be affected in cold places.
  • When comparing daily, look for environmental differences: Check if the storage location was different yesterday and today.
  • Avoid extreme environments: Treat a watch as a precision instrument designed for everyday use.
  • For used watches, usage environment is also information: Whether it was exposed to excessive environments is an important check.

⑦ Concluding after only one day's measurement is like deciding the culprit after only watching one episode

Kenji
So, how many days should I observe the daily rate?

I was about to lecture my watch just looking at yesterday's number.
"You lack stability," I'd say.
Appraiser
Rather than judging based on just one day, you'll want to observe it for several days to confirm the trend.

For example, compare it to a reference time at the same time every day.
Record how many seconds it gained or lost.
By collecting this data for several days, you'll start to see averages and trends.

It would be too soon to accuse only the suspicious person who appeared in the first five minutes of a mystery drama, wouldn't it?
Kenji
Indeed.
People wearing sunglasses in the first five minutes are usually suspicious, but they aren't necessarily the culprit.

Moreover, truly suspicious people usually pretend to be good people and serve tea in the beginning.
Recommended notes when measuring daily rate
  • Measurement date/time: Check at the same time as much as possible every day.
  • Difference from reference time: Record how many seconds it gained or lost.
  • Wearing time: Note how many hours it was worn on the wrist that day.
  • Storage position: Memo the orientation, such as dial up or on its side.
  • Winding status: Check if it was hand-wound or sufficiently moved if automatic.

⑧ Average daily rate is the watch's "report card for a few days of its life"

Kenji
So, I should look at the average.

Gathering data like +5 seconds yesterday, -8 seconds today, +3 seconds tomorrow...
Is it like creating a life report card for the watch?
Appraiser
That's right.

Rather than just a single day's number, look at several days to confirm the average and trend.
Does it gain a little bit every day, or does it fluctuate greatly day by day?
How do the numbers change if you alter its usage?

Looking at it that way makes it much easier to realistically assess the watch's condition.
Kenji
I see.
It's dangerous to decide "this person is suitable for singing" after just one karaoke session, isn't it?

Some people are only good at the chorus, and conversely, some leave everyone behind during the chorus.
Appraiser
(People who leave everyone behind during the karaoke chorus need tempo adjustment more than a watch...)
What the average daily rate reveals
  • Overall trend: Shows whether it tends to gain or lose time.
  • Magnitude of fluctuation: Reveals if day-to-day differences are large or small.
  • Relationship with usage conditions: Shows how numbers change with wearing time and placement.
  • Material for consultation: Makes it easier to explain to a specialist shop.
  • Information for buying: Makes it easier to check the current operating condition of a used watch.

⑨ "Daily rate ±◯ seconds" should be considered with measurement conditions

Kenji
Sometimes when I look at used watches, it says "daily rate ± so many seconds," right?

Is that the watch's absolute self-introduction?
Like, "Hello, my daily rate is +7 seconds. My hobby is walking."
Appraiser
As a self-introduction, that's a bit short on information.

The daily rate notation is important, but you also need to see under what conditions that number was measured.
Was it measured flat, was it a value measured by a machine, or was it the result of actually wearing it on the wrist?

Looking only at the numbers is like judging the taste of food solely from a picture.
Kenji
Judging the taste of food solely from a picture...
Indeed, sometimes the photo looks like high-end French cuisine, but the taste leans towards cafeteria curry.

Well, cafeteria curry is strong, though.
Things to check in daily rate notation
  • Measurement method: Timographer measurement or measurement closer to actual use?
  • Measurement position: In what orientation was the value measured?
  • Measurement period: Is it a snapshot value or a trend over several days?
  • Winding status: Was it measured in a fully wound state?
  • Seller's explanation: Can they specifically explain what the numbers mean?

⑩ When buying, ask "How was it measured?" rather than "What's the daily rate?"

Kenji
So, when buying a used watch, what should I ask?

"Does this watch reliably show up for work every morning?"
"Does the second hand have a habit of being late?"
"Is its relationship with the minute hand a good one?"
Appraiser
You're acting too much like an interviewer.

In reality, you should ask like this:
"What is the current daily rate?"
"Under what conditions was that measurement taken?"
"What is the potential difference that might occur during actual use?"
"If a significant deviation occurs after purchase, where can I seek advice?"

More important than the numbers themselves is to look at the specificity of the explanation.
Kenji
I see.
Just asking "What's the daily rate?" is as blunt as asking "What's your annual income?" on a group date.

First, it's about character... no, it's about the measurement conditions.
Question template before purchase
  • What is the current daily rate?
  • Under what conditions was that daily rate measured?
  • Do you know the watch's position and winding state during measurement?
  • Is it possible for the daily rate to change during actual use?
  • If significant gains or losses occur, where can I seek advice?
  • Is it okay to confirm the daily rate after using it for a while post-purchase?

⑪ Before selling, a daily rate memo becomes the "watch's health diary"

Kenji
Conversely, what should I do when selling a watch?

Will it get the message across if I just say, "This one is generally well-behaved"?
Like a kindergarten teacher.
Appraiser
The sentiment is understood, but specific information is more impactful in an appraisal.

For example, the daily rate over the past few days.
How long it was worn on the wrist.
In what position it was stored.
When the deviation started to become noticeable.

Having such notes serves as a reference for checking its condition.
It's like a health diary for the watch.
Kenji
A health diary...
Like, "Today's second hand: slightly forward-leaning. Good appetite. Good relationship with minute hand."

This is starting to sound like a pet care log.
Daily rate information to compile before selling
  • Deviation over the past few days: How much gain or loss there is
  • Wearing condition: How much it was used daily
  • Storage position: Dial up, sideways, inside a watch case, etc.
  • When noticed: When the deviation started to become noticeable
  • Inspection history: Has it recently undergone an accuracy check?

⑫ Remember it as "align, measure, accumulate, average"

Appraiser
When checking the daily rate, it's good to remember it as align, measure, accumulate, and average.

First, align the measurement conditions as much as possible.
Next, measure at the same time of day.
Then, accumulate several days' worth of records.
Finally, look at the average and trend.

Doing this makes you less likely to be swayed by a single day's number.
Kenji
Align, measure, accumulate, average.

I used to be look, panic, doubt, make the watch apologize.
Appraiser
Before making the watch hold a press conference to apologize, first, record it.

The daily rate is important information for understanding a watch's condition, but it's not something to be judged by a single day's number.
Align the conditions, look at several days' worth, and judge based on the trend.

That way, it becomes easier to make a calm judgment whether you're buying a used watch or selling one you own.
4 steps for daily rate checking
  • Align: Align measurement time, storage position, and winding state as much as possible
  • Measure: Check the difference from the reference time at the same timing
  • Accumulate: Gather records not just for one day, but for several days
  • Average: Judge by looking at the overall trend

Conclusion: "Daily rate" is not a one-shot deal, but a trend over several days

Appraiser
The daily rate is an important indicator for understanding a watch's condition.
However, it doesn't necessarily show the exact same number every day.

Positional variation, winding amount, wearing time, temperature, measurement method.
It can change due to various conditions.

Therefore, whether you're looking at a used watch or selling one you own, don't make a judgment based on a single day's number.
Look at several days' worth of records and judge by the average and trend.

Here's how to remember it:
Don't tell your watch to come to work with the same enthusiasm every day.

Even the second hand has its own environment, you know.
Kenji
Understood.
From now on, I won't panic immediately if it's +5 seconds yesterday and -8 seconds today.

First, I'll align the conditions, measure for several days, and look at the average.
And before making the second hand produce a shift schedule, I'll take notes.

However, my daily rate on Monday morning is probably -3 hours.
Appraiser
(Adjusting Kenji's own accuracy, I'd like to start with him going to bed early...)
4 things you can do starting today to avoid panicking about "daily rate"
  • Don't judge the daily rate based on just one day; look at the trend over several days.
  • Align measurement time, placement, and winding state as much as possible.
  • When buying a used watch, ask about the measurement conditions, not just the daily rate number.
  • Before selling, make a note of the gains/losses over the past few days.
NEXT EPISODE
Episode 27: Is that "chronograph" just a stopwatch when you press it?
~ The watch world's "Don't try to fix appliances by mashing all the buttons" problem ~
  • Start, stop, reset. If you press them in the wrong order, the owner gets more confused than the watch
  • Chronograph hand, totalizers, reset position. Even if it looks like it's moving, it doesn't necessarily return correctly
  • The appraiser's analogy: The "Don't press all the microwave buttons to become a good cook" theory explodes
Next time, Kenji issues a no-button-mashing order to the chronograph!
※Next episode preview is a dramatization. However, checking the chronograph's operation is quite important for both choosing a used watch and appraisal.

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