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DivinylsFan  The age spans are saved in Options.ini, not UserPresets, which is for custom recolors you've saved in Create a Style.  And no, there's no way to retrieve the old age stage lengths from within a save because they're not save-specific.  You could however load the save, find a sim whose age you know more or less (maybe they were ready to age up or just had), see how many days they're missing, and adjust accordingly.  I realize this is tedious, but there isn't a better approach.

Season length is also in Options.ini, but I can think of two possibilities: that you're currently using the same season length you were then, or that a mod (perhaps NRaas Tempest) saved the season lengths for you.  NRaas mods' settings are save-specific, although I haven't used Tempest myself, so that part is only speculation.