In larger hoods like my uberhood, or my test of time hoods, I used a system of 1 year = 1 day, so;
Baby: 2 days (0-2)
Toddler: 3 days (3-5)
Child: 6 days (6-11)
Teen: 6 days (12-17)
YA, either in hood or at uni: 8 days (18-25) (each semester at uni is 48 hours, so 2 days (1 semester) at uni is equivalent to 1 day in the main hood)
Adult: 24 days (26-49)
Elder: (50+)

By blowing out the cake or not (when the clock hits 18 at the last day).

Hat's mod is very long in age span, I don't think it's that popular at all.

I've always used Inge's one and customised it myself.

For a while I had 2 days = 1 human year for all ages up to adult and then 1 year = 1 day from then on, to simulate that the years go by faster when you're an adult! But actually they ended up ageing and dying too soon, so I changed to 2 days per 1 human year. I keep pregnancy as it is, I always just figured that pregnancy for sims lasts longer.

However... now I am also starting to find THAT age span a little too short! My sims barely have time to form relationships and procreate! Where is the variety? So I am eyeing up Hat's. Or perhaps an in between, with 3 days per human year. The very nice part about Hat's mod is that there is already an adjusted ACR controller for it, so I am tempted simply to try that one first.

Aging is modded in my game thanks to Inge's aging mod. My settings are the almost the same except that adults become elder at 60. I like generational play.
I'll hit 50 in a few years and even if I'm not that young, I don't feel like I'll be an elder anytime soon. People often think I'm in my thirties.

ACR is not modded but I got pixels who got pregnant at 54 simdays old (I play with silent pregnancy and risky woohoo).
Pregnancy lasts 48 hours.

shipped version aging without cheats seems kind of weird; since each Age has the option to transition a day early.
age lengths without the "early" transitions::
baby: 3 sim days.
toddler: 4 sim days.
child: 8 sim days.
teen: 15 sim days.
adult: 29 sim days.
elder: 9 to 31 sim days.

age lengths with all "early" transitions::
baby: 2 days.
toddler: 3 days.
child: 7 days.
teen: 14 days.
adult: 28 days.
elder: 9 to 31 days.

real life equivalents::
baby: months 0 through 18; about 6 months per sim day.
toddler: month 18 through age 5; roughly 14 months per day.
child: ages 5 through 13; about 1 year per sim day.
teen: ages 13 through 20; roughly 6 months per day.
adult: ages 20 through 55; roughly 15 months per day.
elder: age 55 and above.

I don't know about any of you, but if I had a real life baby that wasn't walking or even crawling by age two, I'd be concerned!

did some changes to "real life equivalents".

Lol hence why I say 2 days = 12 months!

One of the reasons why my husband and I made our age mod the way we did was that irl babies can be walking as early as 6-7 months. Yes, this is rare, but there's plenty of WHO data on it. I think the average age for walking is about 12 months and the average for talking is more like 2 years (it's usually a long process as they build their vocabulary and develop basic grammar skills). Both of our irl babies were crawling by 5 months, though apparently the average is more like 8-9 months. So our toddler stage starts at the real life equivalent of 8-9 months. Most of our sim toddlers do learn to walk before they learn to talk, but that's mostly because it's a more useful skill and seems to take significantly less time to teach (I've always found teaching a sim toddler to talk takes freaking forever!).

I was once told that I finally learned how to walk at 24 months of age, but I had myopia thus I couldn't see things well.

Right, yeah. It would definitely be a sign of some issue like that.

I knew a lady who's daughter started speaking at 5 months as well! It was only "mama" / "dada," but still kinda freaked her out a bit.

Apparently I was speaking in full sentences at just under two years old, that I believe even that is a bit earlier than average.

my cousin was 1 in July and she just scoots on the floor is that bad?

I was 13 months before I learned to walk. My mother was 18 months! Mainly because my grandmother kept her in a crib so she wouldn't get dirty.

Around a year old is average. I had a cousin that learned at 7 months. I scooted on the floor as well. My daughter was about the same age as I was. Talking is a cumulative process, that gets better over time, mama and dada are usually first words, and occur fairly early, and then there are more words, two words together, main words in a sentence, and then actual complete sentences.

As far as being an old, gray haired grandma, my godmother became a grandmother at 31! She was 16 when her daughter was born, and that daughter was 15 when her son was born.

I am 51, fixing to be a grandmother for the second time, and no gray hairs, thank you

Depends on who you ask. But technically scooting is in the same category as crawling.

oh ok so she's not that far behind for her age?

Yeah, every kid grows up on its own schedule.

Just be alert for patterns that might indicate a larger problem. Like, if she scoots everywhere and her legs look underdeveloped or she holds her feet at funny angles, that might indicate a problem with her legs; if she has a hard time picking things up and hanging onto them when she clearly wants to, too, that might indicate a problem with muscle coordination. If she's behind on locomotion and talking and potty-training and a bunch of other benchmarks, that may mean a developmental disorder, or insufficient interactions encouraging her to develop (like gdayars's mother being stuck in her crib), or some other larger thing.

Generally when a preverbal child has a problem, it affects multiple areas of their development. That's why you keep track of benchmarks; being behind on one or ahead on another isn't a big deal, but keeping track and having a rough timeline to compare to makes parents more likely to spot problem areas and deal with them before they have a serious impact on the child's quality of life.

well she can stand up if she holds on to the couch and can say a few words so i'm sure she's fine.

Yes, and there is just no way to make the limited age categories "fit" with real life. The Child is hard enough (from 3or4 years to 12) but teens are worse; a 13 year old is NOTHING like 19 year old - 6 short years (RL) and so many changes!

Shortly after TS2 came out, I said I wanted a preschool stage and a preteen stage. I think I also said I wanted a "middle aged" category, but TS3 basically added that by making young adult a normally playable life stage, and even added in the whole "midlife crisis" scenario. TS4, of course, was a huge disappointment when instead of expanding on things like this, it just went backwards by removing toddlers! (I know they've since added toddlers. But I'm not holding my breath for preschool/preteens!)

i think toddlers should have nursery (kindergarten for you americans)

Kindergarten is for 5 year olds, or 4.5 year olds (depending on when their birthday falls in the year). Pre-K starts a year before that in places that have it. But even 3.5 year olds aren't "toddlers" anymore.

oh ok i've gotten confused then i thought it would be for toddlers as my other cousin who is 3 is has gone to school for a year now i think.

I'm in Canada, actually, but our system is quite similar to the one in the USA. We have preschool which is for ages 3-4, though I think sometimes 2.5 year olds can start preschool. It's not required and it's also usually not free, so not everyone sends their kids to preschool. Kindergarten is required, though, as well as being free. As I said, it starts at age 5 and is the year before grade one. Some areas also offer pre-K, which is a year before regular Kindergarten. My understanding is that it's a lot like a year of free preschool, offered through the school system rather than a private provider.

My kids attended a free drop-in preschool program which differed from a regular preschool in that the parents were required to stay with their kids rather than dropping them off. My older son also attended a short free preschool program offered by a local church.