The 2000s were the worst decade in US stock market history.

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It took 13 years to recover from the peak of the 2000 dot-com bubble.
While that is a short period compared to the 25 years it took to recover from the Great Depression,
the story changes if you use dollar-cost averaging.
According to my GPT check, if you started long-term investing at the peak of the Great Depression
and used installment buying + dividend reinvestment, you would break even in 5 years and 7 months;
however, for the dot-com bubble + subprime mortgage crisis, it takes 9 years and 6 months.
The 2000s could arguably be viewed as a once-in-a-century crisis,
and it feels like a relief that it has only been about 20 years so far.