11 standard deviations

Hello. I am new here...my first post.

Anyway, last week in the stock market the financials rallied ~13%. I read that this is 11 standard deviations. How can I find out how long this event occurs in years? I know it is VERY, VERY rare. I read that 4 standard deviations is about 31,000 years. Though I am not sure if this is correct.

Thanks for your help.