June 21st, 365, the date of the big Mediterranean earthquake and tsunami, lived in infamy for a few centuries before fading. Maybe the trick is a catchy rhyme; the '5th of November' thing is still going strong over 400 years later.

"FDR", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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June 21st, 365, the date of the big Mediterranean earthquake and tsunami, lived in infamy for a few centuries before fading. Maybe the trick is a catchy rhyme; the '5th of November' thing is still going strong over 400 years later.