(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.