I play with a custom 3 week season length so I can have all of the 12 months (1 week equals 1 month). My sims lifespan is tied to the seasons to make sure that they always age up on the day they were born (for example, if a sim was born on 2nd of March they will age up on the 2nd of March next year). An entire seasonal year is 84 days so it's 84 days for toddlers-teens (babies are included with toddlers), 168 for young adults, 252 for adults and 168 for elders. That's 840 sim-days and 10 seasonal years. Sometimes when I'm bored I change the season length to 1 week. Then I choose the most important week out of the three (usually the one with a birthday or a fun holiday) and pretend the next two happened offscreen (hope that makes sense :tongue:).
I've been playing like that for over 9 months and so far it's the only way that works for me because it bugs my perfectionist mind when sims age up on different dates XD It's not ideal and I'm still annoyed with the fact that they have a lifespan of a dog or a cat (as in their "growing" years don't sync with "seasonal" years and a baby born in summer will celebrate their next birthday at the age of 7) but it still works better then the options provided in game.
