(If this is not the correct place can you tell me where?)

So I wanted to learn how to make mods for the Sims 4 and this stemmed from small things that I wish I had and one of those is a way to keep track of years in the Sims 4. I want to keep my aging realstic:

Newborns
4m years

Infants
5m-11m years

Toddler
1-5 years

Child
6-12 years

Teen
13-19 years

Young Adult
20-29 years

Adult
30-59 years

Elderly
60-Death

So I wanted to try and mod the calender in the Sims 4 but I dont know at all where to start. The mod would work like adding a calender feature in the phone. I havent found any tutorials on here about modding anything like that and I dont know where to look.

I also want to know.

Honestly, there's no reason because of how absurd and unrealistic are the in-game lifestages made.... those jumps from child to a teen that is almost a copy of young adult, and from healthy (quite) 45 yo adult into the crooked 80+....that pisses me off. At least, they could use the model of adult, but with grey hair available only at 60+ as a mid-stage and enumerate it into the tuning, it is not that hard....but they still prefer to fix the issues already claimed as fixed by
themselves though they're not))) and so on...sadly. Example: my own mods folder....20 Gb's - "Tweak Fix" (Twin Peaks inspired), Cloths - 5 Gb, Build - 60 Gb, Misc - less than 1 Gb.