10 ms·

No, birthdays are 1 indexed. Your Nth birthday is the day you turn N years old. When you're 1 year old, you've been alive for 1 year, not 2 years.

brianzelip 4y ago
So how old is a not-yet-1-year old?
- atwood22 4y ago
  N days or N months depending on how old the baby is.
  - randomdata 4y ago
    And it turns out that 0 days, 0 months is 0 years.
  - rcoveson 4y ago
    And before an hour has even passed, we'd probably say "minutes old" or perhaps "not even an hour/day old", all to avoid saying "zero days/months/years old". But some might still say zero days old, and they'd be both understood and correct (at least logically if not stylistically). That's the "implicit zero" everybody is talking about. We avoid saying it, but that's just a convention of communcation. Logically it's there. You're zero days old before you're one day old.
- nomel 4y ago
  Elapsed time timers start at 0. Time is continuous. The elapsed time being “out of the womb”, that we call “age”, starts near 0. Five minutes after birth, the baby has been in the world for, or it’s age is, five minutes. If someone asked how old a new baby is you could hear “3 weeks”. Another definition might be from conception. But birth being “one year old” is illogical. The sperm didn’t even exist yet, one year before birth.
- xxs 4y ago
  Your mistake is using years - use milliseconds (or nanoseconds) when you wish to express a duration. Years don't even have the same duration/length (leap years, and leap seconds)
randomdata 4y ago
The moment you are born you are 0 years old (or perhaps 0.75 years old, but we don't usually recognize that). We count from zero in this case, at least implicitly. In some cultures you are considered 1 the moment you are born, so the zero indexing isn't universal here, but typical in North America as noted earlier.
- atwood22 4y ago
  No, we don't count from 0. That's like saying we start counting a baker's cup from 0 because you can have half a cup.
  - randomdata 4y ago
    If we (speaking as a North American) count from 1, does that mean other cultures (e.g. Korean) count from 2?
    - atwood22 4y ago
      No, it just means we have a different notion of what a year is in regards to age. Similar to how different cultures can use different units of measurement for length, mass, etc.
      - randomdata 4y ago
        Yes, exactly. One of which carries an implicit zero indexing. The date of birth doesn't disappear just because you decided to use a different measuring device.
        atwood22 4y ago
        No, it doesn’t carry an implicit 0 index. Measuring age (in the West) is like measuring distance. You start at 0, but that doesn’t mean the first item is at index 0.
        4y ago
csours 4y ago
Your birth day is the day you are born. Your first birthday is the first anniversary of your birth day. We celebrate the anniversaries of our birth day.
- treis 4y ago
  Yep, clearer in Spanish. They say cumpleaños which literally means completed year.
rcoveson 4y ago
No, old calendar systems are one indexed. In those system, there is literally no year zero; the first year is year one. This leads to crazy things like year 100 being part of the "first century" and year 101 being part of the "second century". That is not the case with age or birthdays which are, thankfully, zero indexed. The first year of human life is age=0, birthdays=0.
- lupire 4y ago
  It's not "crazy". No one care about which century X00 is. The term "century" doesn't have enough sig figs. X00 is "the turn of the century".
  - rcoveson 4y ago
    If you don't care then sure, it's not crazy, but if you did care then believe me, it is crazy. Crazy enough that astronomers[0] and software engineers[1] rebelled against the historian's practice and renamed the years preceding 1 AD in the proleptic gregorian calendar year 0, year -1, year -2, et cetera. A major benefit of this is it allows the leap year pattern to stay consistent and the rule to remain legibile for all years, going back before 1 AD. It's also nice because it lets us say "the 90's were the last ten years of the 20th century" and be correct. 0. https://en.wikipedia.org/wiki/Astronomical_year_numbering https://en.wikipedia.org/wiki/Astronomical_year_numbering 1. https://docs.oracle.com/javase/8/docs/api/java/time/temporal/ChronoField.html#YEAR_OF_ERA https://docs.oracle.com/javase/8/docs/api/java/time/temporal...
- deleted 4y ago
  [deleted]
- samatman 4y ago
  So that we don't create more falsehoods programmers believe about dates, ISO has defined decades and centuries as starting with 0, not 1. So as far as your job is concerned, that's when they start. Hope that helps.
wruza 4y ago
Haha, this thing is messed up. Your "first birthday" is technically second, because the first was at your, well, day of birth. But we people love to complicate things and count 1st birthday as a number of annual celebration events after the first mm-dd of birth. Off by one as it is.

brianzelip 4y ago

So how old is a not-yet-1-year old?

atwood22 4y ago
N days or N months depending on how old the baby is.
- randomdata 4y ago
  And it turns out that 0 days, 0 months is 0 years.
- rcoveson 4y ago
  And before an hour has even passed, we'd probably say "minutes old" or perhaps "not even an hour/day old", all to avoid saying "zero days/months/years old". But some might still say zero days old, and they'd be both understood and correct (at least logically if not stylistically). That's the "implicit zero" everybody is talking about. We avoid saying it, but that's just a convention of communcation. Logically it's there. You're zero days old before you're one day old.
nomel 4y ago
Elapsed time timers start at 0. Time is continuous. The elapsed time being “out of the womb”, that we call “age”, starts near 0. Five minutes after birth, the baby has been in the world for, or it’s age is, five minutes. If someone asked how old a new baby is you could hear “3 weeks”. Another definition might be from conception. But birth being “one year old” is illogical. The sperm didn’t even exist yet, one year before birth.
xxs 4y ago
Your mistake is using years - use milliseconds (or nanoseconds) when you wish to express a duration. Years don't even have the same duration/length (leap years, and leap seconds)

randomdata 4y ago

The moment you are born you are 0 years old (or perhaps 0.75 years old, but we don't usually recognize that). We count from zero in this case, at least implicitly. In some cultures you are considered 1 the moment you are born, so the zero indexing isn't universal here, but typical in North America as noted earlier.

atwood22 4y ago
No, we don't count from 0. That's like saying we start counting a baker's cup from 0 because you can have half a cup.
- randomdata 4y ago
  If we (speaking as a North American) count from 1, does that mean other cultures (e.g. Korean) count from 2?
  - atwood22 4y ago
    No, it just means we have a different notion of what a year is in regards to age. Similar to how different cultures can use different units of measurement for length, mass, etc.
    - randomdata 4y ago
      Yes, exactly. One of which carries an implicit zero indexing. The date of birth doesn't disappear just because you decided to use a different measuring device.
      - atwood22 4y ago
        No, it doesn’t carry an implicit 0 index. Measuring age (in the West) is like measuring distance. You start at 0, but that doesn’t mean the first item is at index 0.
        4y ago

csours 4y ago

Your birth day is the day you are born. Your first birthday is the first anniversary of your birth day. We celebrate the anniversaries of our birth day.

treis 4y ago
Yep, clearer in Spanish. They say cumpleaños which literally means completed year.

rcoveson 4y ago

No, old calendar systems are one indexed. In those system, there is literally no year zero; the first year is year one. This leads to crazy things like year 100 being part of the "first century" and year 101 being part of the "second century". That is not the case with age or birthdays which are, thankfully, zero indexed. The first year of human life is age=0, birthdays=0.

lupire 4y ago
It's not "crazy". No one care about which century X00 is. The term "century" doesn't have enough sig figs. X00 is "the turn of the century".
- rcoveson 4y ago
  If you don't care then sure, it's not crazy, but if you did care then believe me, it is crazy. Crazy enough that astronomers[0] and software engineers[1] rebelled against the historian's practice and renamed the years preceding 1 AD in the proleptic gregorian calendar year 0, year -1, year -2, et cetera. A major benefit of this is it allows the leap year pattern to stay consistent and the rule to remain legibile for all years, going back before 1 AD. It's also nice because it lets us say "the 90's were the last ten years of the 20th century" and be correct. 0. https://en.wikipedia.org/wiki/Astronomical_year_numbering https://en.wikipedia.org/wiki/Astronomical_year_numbering 1. https://docs.oracle.com/javase/8/docs/api/java/time/temporal/ChronoField.html#YEAR_OF_ERA https://docs.oracle.com/javase/8/docs/api/java/time/temporal...
deleted 4y ago
[deleted]
samatman 4y ago
So that we don't create more falsehoods programmers believe about dates, ISO has defined decades and centuries as starting with 0, not 1. So as far as your job is concerned, that's when they start. Hope that helps.

wruza 4y ago

Haha, this thing is messed up. Your "first birthday" is technically second, because the first was at your, well, day of birth. But we people love to complicate things and count 1st birthday as a number of annual celebration events after the first mm-dd of birth. Off by one as it is.