When you mix varying lifespans and maturation rates, immortality, age-changing, time-travel, altered time rate areas, stasis / hibernation, and body-jumping, a person could have as many as four distinct ages.


Chronological age - Very simple and, if in home universe and native-time, easy to objectively measure for legal definitions - from the person's birth date to current date. CK3 mod-speak term is just simply 'age'.

Experienced-time age - How old is the person's mind? How much time has the person experienced? Time travel, altered time rates, and stasis can diverge this from chronological age. This age can't really be objectively measured by a 3rd-party observer unless the circumstances are simple. There is no applicable CK3 mod-speak term.

Physical age - How old is the person's body? Immortality (age-freezing) or age-changing, as well as time travel and altered time rate areas can diverge this from chronological age. CK3 mod-speak term, if immortal, is 'immortality_age'.

Human-equivalent physical age - How old is the person's body in human-equivalency-terms? Being of a (or jumping into a body of a) species that ages differently from humans will diverge this from physical age. There is no applicable CK3 mod-speak term. Though there may be something internal as an age has to be chosen / calculated from the age, immortality_age, and the dozen or so maturity (NCharacter), old-age (NOldAge), and lifespan related (NPortrait) defines when generating the character portrait.


For body jumpers: Usually the birth date of the current host body is more known and used. In rare scenarios such as a powerful PL-X supervillain getting his way for over 1000 years, who's infamy greatly dwarfs the fame or infamy of the the mind that was previously in the host body, the chronological age is based on the birth date of the occupying mind's original body. In the case of a body snatching pseudo-immortal where the date of birth of both the host body and the occupying mind (or the mind's original body) are well known, the person could have two distinct chronological ages.

Universe jumpers and frequent time travelers: Frequent universe hopping and universe jumping, especially when such travel is uncontrolled, will result in a chronological age that can not be determined as there is no fixed frame of reference in time, or universe, to be able to determine a chronological age. In this instance a guess of the physical age may be used for legal stuff instead of chronological age, if going fully legit and not using forged identity documents.

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Chronological age - In-universe legal definitions. Legal adult age, legal marriage age. Age benchmarks tied to civil rights, privileges, responsibilities. Barring extremes or special circumstances.

Experienced-time age - Nothing. There is no time-travel or altered time rate areas in the game or any mods (yet), And if things do pop-in that use any of those things, this type of age is difficult to objectively measure, so I think nothing should use this age-perspective.

Physical age - Attraction cut-off age, age-based fertility adjustments, age-related prowess loss. For physical and portrait parameters only - toddler age, childhood age, adolescence age, adult age.

Human-equivalent physical age - Portrait appearance / DNA. Also, the undress lock-out, since this is for real-world anti-child-pornography legal issues. To plug the defines loophole of people altering human lifespans and maturation rates in the defines to get around the current absolute physical age based undress lockout.

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Species transformation to a species that ages at a different rate while maintaining human-equivalent physical age, followed by a body-jump trip back in time 'reset' or 'rewind'.

A half-elf is transformed by a magical water crystal into the world's first aquatic elf. Half-elves have double the lifespans of humans, and full-elves have sixteen times the lifespan of humans. This fantasy world has no immortality and no early maturation. All PCs in this campaign world start between the ages of 11 and 13 (double for half-elves 22-27; tanner stage 2 puberty) and are the first in over 1000 years to manifest magical powers. PC races were limited to human, cat-folk (no extended lifespan), and half-elf (double-lifespan)

Before transformation:

• Lysanthir is age 25yr 8mo at the time of transformation. His chronological age is 25yr 8mo.
  
• Lysanthir's experienced-time age is the same as his chronological age of 25yr 8mo - no time-travel or altered time rates have occurred.
  
• Lysanthir's physical age is also 25yr 8mo.
  
• Lysanthir's human-equivalent physical age is 12yr 10mo as half-elves have double the lifespan, but also need double the time to mature.

After transformation:

• Lysanthir's chronological age is 25yr 8mo.
  
• Lysanthir's experienced-time age is the same as his chronological age of 25yr 8mo - no time-travel or altered time rates have occurred.
  
• The physical age of Lysanthir's aquatic-elf body is 206 years as that is the age needed to maintain human equivalent age of 12yr 8mo with a 16x lifespan and maturation time.
  
• The aquatic elf body Lysnathir transforms to is aged in such it has the same human-equivalent age as prior to transformation. So Lysanthir's human-equivalent physical age remains at 12yr 8mo.

Now a divine artifact throws the party back in time, and into their original bodies at the start of the campaign. Mental improvements to character remain, but physical improvements are reset:

• Lysanthir's chronological age resets to 25yr 0mo - time travel has occurred, rolling back to beginning of campaign
  
• Lysanthir's experienced-time age is a 26yr 4mo - both time travel and body-jump has occurred
  
• Lysanthir's physical age is 25 years, back in sync with chronological age
  
• Lysanthir's Human-equivalent physical age is reset back to 12yr 6mo - put back into his own half-elf body at the start of the campaign.

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Involuntary body jumping into a species that ages differently from humans with no synchronization of human equivalent physical age, eventual return to home universe, then undoing the body jump..

Josef and Jacob El-zein, 15 year old fanatic-christian autistic-weirdo identical twins (only thing in common with the real twins of the same name, is the name), get exposed to the masquerade, become werewolves, gain body-jumping powers and transition to universe-hopping rotating-GM campaign. In a sci-fi research lab on a very high-G watery mid-planet oceanic gas-dwarf planet occupied by a intellectually enhanced near-immortal slave-race, their power involuntarily activates and they involuntarily body-jump into two of the young natives.

How the StarView age:

• 0-15 - age at normal human rate. Chronological, physical, and human-equivalent physical ages are all the same during childhood.
  
• 16-159 - Aging slows to 1/16 the normal human rate. Human-equivalent physical age is 16-24. The 'youth zone' (roman perspective) is expanded from 9 years to 134 years.
  
• 160-399 - Aging freezes in during this time. Human-equivalent physical age is 25 for this entire period of 240 years.
  
• 400-799 - Aging resumes at 1/16 normal human rate. Physical age and human-equivalent physical age are 16-to-1 (400 years old is human-equivalent of 25, 800 is equiv of 50). There is zero risk of aging related decline during this phase, but physical signs of aging are present.
  
• 800-1199 - Aging related decline can happen, but is fairly low. Even without advanced technology, there is usually not enough decline to accumulate notable disability. Human equivalent physical age 50-74.
  
• 1200-1599 - Notable age-related disability accrues. Human equivalent physical age 75 to 99.
  
• 1600+ - Major disability is accrued. Death by pure old age at 1850 to 2150 years (human equivalent 115 to 135) without advanced technology.

When the twins body jumped:

• Josef and Jakob's chronological age cannot be determined because they are time and universe hopping all over the place.
  
• Josef and Jakob's Experienced-time age is 15 years 3 months
  
• Josef and Jakob's physical age is 17 years 1 months - they jumped into bodies that were slightly older than their original bodies.
  
• Josef and Jakob's human-equivalent physical age is 16 years 1 months - their new Starview bodies has entered the 2nd life phase where their human-equivalent aging dramatically slows.

When the twins finally return to their home universe 15 months later:

• Josef and Jakob's chronological age is 15 years 4 months - they arrived back in the original universe about a month after they left.
  
• Josef and Jakob's experienced-time age is 16 years 6 months - they have been time traveling and universe hopping for 15 months, but arrived home 1 month after they left, so the chronological to experienced age difference is reduced to 14 months.
  
• Josef and Jakob's physical age is 18 years 4 months
  
• Josef and Jakob's human-equivalent physical age is 16 years 2 months

A few days after returning, after being near the epicenter of a fight between the masquerade-entity and an Aztec sun-god, their body-jump was somehow undone:

• Josef and Jakob's chronological age is 15 years 4 months.
  
• Josef and Jakob's experienced-time age is 16 years 6 months.
  
• Josef and Jakob's physical age is back in sync with chronological age, 15 years 4 months.
  
• Josef and Jakob's human-equivalent physical age is also back in sync with chronological age, 15 years 4 months.

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Immortals confined in an 1000x accelerated time chamber (nearly 20 years experienced for each week elapsing outside, opposite of the movie time-trap)

A super-villainous scientist abducts and locks a pair of sixteen year old best friends in a 1000x accelerated time field chamber for a 0.02 years (a week plus 7.35 hours), to prove his immortality serum is safe and effective to potential buyers. Two and best friends as locking one alone will likely result in insanity and probable suicide, and anything short of best friends may kill each other, and dead subjects would ruin the demonstration. Teens are chosen as aging even just a few years is obvious. A 25 year adult that ages at 10% (2 years) is not very discernible. A 14-16 year old that ages 2 years is very obvious. Younger than 15-17 may not adapt to supporting themselves super-long-term alone. The mad scientist wants to prove zero aging, or at least less than 5% (statistical significance in scientific studies - 5 percentile).

At the start of the experiment:

• They are issued the experimental 'immortality serum' at 16yr 8mo and 16yr 10mo.
  
• They are held for a month before the start of the accelerated time field confinement phase. At the start of confinement, one is chronologically 16yr 9mo and the other is 16yr 11mo.
  
• The confinement for 0.02 years of real-time in a 1000x accelerated time field chamber (20 years experienced) begins

After the end of the experiment:

• Chronological age advances by just one week, so they are chronologically still 16 years of age
  
• Experienced-time age advances by almost 19.15 years, rounded to 19 years 2 months. Experienced ages are 36yr 11mo and 37yr 1mo
  
• Physical age remains the same, at 16yr 8mo and 16yr 10mo, due to being immortal and completely ageless.
  
• Their human equivalent physical age remains synchronized with their physical age as no altered-lifespan is involved.

Aftermath:

• The teens are rescued by the PC heroes nearly at the time of pre-programmed release. The teens experienced 19.15 out of the pre-programmed 20 years. They come out alive and healthy. They destroy the mad scientist's labs, but the mad scientist himself gets away. There are some mental issues with the teens, particularly acquired significant separation anxiety, but they are mostly functional.
  
• The two teen best friends are both male, so no babies are born in the accelerated time chamber. They are not gay so nothing other than masturbation occurred in the time chamber. They do become as close as close identical twins though.
  
• In the superhero universe where this scenario occurred, 10% of all supers are immortal / ageless. The majority of the immortal age-freeze between 16 and 24. Age freezing outside of 12-30 is rare, and there are no documented cases of age-freezing outside of the 6-60 range. Other than some 6-7 year old immortals, most gain the ability to mostly function as an adult by age 20 though some frozen in the 8-11 (most 6-7) range may need extra help or time. Therefore unless under court incompetency labels, all ageless supers gain their civil rights, privileges, and responsibilities according to their chronological age, not their physical age. Therefore on rescue, these two teens are still legally minors.
  
• With some counseling, the two teens re-integrate into society. Two years later, they graduate high school and completely crush their SAT and college placement exams as the mad scientist provided them with a crap ton of books and computer resources in their confinement chamber and their powerset includes superior (but not super) intelligence.
  
• The immortality serum doesn't work.... These two teens manifested their powers during the one-month period between injection and the start of their accelerated time chamber confinement. The serum may trigger natural immortality activation if it is already almost imminent, but it is otherwise complete snake oil placebo.. The mad scientist supervillain just wanting to make trillions and put Terra Amazonia to competitive shame is ostracized as a fraud and becomes a traumatized menacing supervillain wanting death and destruction.
  
• The two teens' powersets are very mild. About a quarter of supers in this world are very low power, just enhanced stats and all-round ♥♥♥♥-superior and easily blend in with society. Being known supers still prevents them from participating in anything elite-competitive though (college sports, professional sports, esports, etc..).
  
• After a two year time jump, the two teens are now legal adults with chronological ages late-18, physical ages late-16 (immortal), and experienced-time ages of just over 39 years old. They still cant legally drink or buy or carry handguns as they are chronologically still under-21.