I play my game in rounds, each round representing 1 real year and lasting 2 sim days. Most of the households, if not all, get played in each round and all are played with aging turned off, so in whatever month their birthday is in I make them one day older.
As I mentioned before, I play my game with months which together make up a season which together with other seasons makes up a year or a round. So, let's say I play the Petit family in January 1981, then the Girard family also in January 1970, but then I move to February 1981 with the Durand family, and once I finish December I start another round.
Let's take the previous example again and show another aspect of my aging and time. Say I finished playing the Girard family which is the last family scheduled for January 1981, I move on to February. So before I start playing the Durand family which is the first family scheduled for February 1981 I age up whoever's birthday is on February. So Fletcher Girard's 56th birthday is on February 1981 and plenty of other VT residents celebrate their birthday on February, I substract one day from all of their lives before I move on to playing the Durand family. But wait, both Lyra Garcia and Andy David celebrate their 18th birthday on February, and unlike Fletcher their birthday is very important to me, because it marks their transition to the life stage of adults.
Before we move on, my life stages go as follows:
Baby stage lasting 1 sim day representing age 0.
Toddler stage lasting 3 sim day representing ages 1-3.
Child stage lasting 8 sim days representing ages 4-11.
Teen stage lasting 6 sim days representing ages 12-17.
Adult stage lasting 42 sim days representing ages 18-59.
Elder stage lasting 1 to 30 sim days representing ages 60-90.
So instead of just substracting one day from their lifespan, I age them up from teens to adults, all of you being simmers I am sure know how to do this. Many of you will move them to the lifestage of young adulthood at this point, but that is discussed on the Education page, so if that's what you're interested in, it's here.
Not much more interesting is happening in February 1981, so let's assume we finished playing all the households schedules for February and move ahead to March. In the beginning of March again, we substract one day from all the March borns lifespans and grow up Rafael Silva who happens to turn 18 to an adult. (It's just a coincidence I'm aging them all up to adults, if we were in April say Amy Roux would turn 4 and become a child). Other than that though, two sims will be giving birth: Desiree Fournier two her twins, a boy and one more unknown, and Halette Simon to her baby girl. If all goes right, I will leave their households with Philip and Collette/Jacques Martin and Aimee Simon and mark their birthdays as March 1981. At this point they are babies, and in March 1982 they will become toddlers.
Another important thing will happen in March 1981: An unknown sim will reach her second trimester of pregnancy. I won't tell you who she is as she doesn't know of it yet and clearly, you readers (Hopefully?) won't know of it until she does. If she reaches second trimester it means she is 4 months into her pregnancy (So this praticular sim got knocked up in December), third trimester means 7 months and we all know when birth happens, so this sim will give birth in September 1981. So in March 1981, I will bump her to second trimester and she will remain on hold until I will bump her to third in June and let her give birth in September.
All of those things will be documented in birthday posts a-la Sullivan Sims (Isn't everything a-la Sullivan actually?) and also announcments on whichever couples succeeded (Or failed not) to conceive.