[2021] My save game went back in years, how do I fix it (Ironman)?

I cannot account for that. Not can I understand how you have a cloud and a local save of the same Ironman campaign.

Is there some backstory here?

FYI cloud saves are visible here:

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Local saves are kept here:
Documents/Paradox Interactive/Stellaris/save games/  

Not for the same campaign, no - whatever the game save setting is at, it saves there for the whole campaign.

Unless you started a new one with the same name, something like that?  

Yes, I'd definitely recommend that for the future!

Very sorry this happened to you, whatever the cause.