I found where it shows how many days are left until age up but I'm not sure how many days have passed. Oddly both sims I created as starting sims in my family show two different age days left. I found...
There is an issue with Sims being started with random days added. This AHQ EA thread refers to the issue https://answers.ea.com/t5/Bug-Reports/OPEN-Age-groups-start-with-random-days-added/m-p/7189326#M77327
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