Finding the spookiest day of the century: A thread
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My 8-year old asked: Dad, what would happen if the full moon was on a Friday the 13th in October?

She's been working through the #Wolfram Language Intro and I thought this was the perfect “real world” application for a kid

We’re about a quarter of the way through the course, and she’s finally getting to the subjects (colors and shapes) that attract her enough to make her push herself.

I found a simple algo for finding Friday the 13ths on StackExchange and modified it to limit findings to October and Full Moons.
The full moon part was shockingly easy, I went to the Wolfram Docs and found a built-in function with one-click and a hover: MoonPhase[]

Once those were added to the algo, my daughter added a Table function to search every year from 2020 to 3020.

Apparently in the next 1000 years Oct 13 only falls on a Friday + full moon 3 times!

At this point I let my daughter go, while I kept tinkering.

Unless you specify a time of day, Wolfram will only return a “Full Moon” result if the moon is full at midnight, but the moon won’t be above the “full” threshold for a full 24 hours.

I then modified my algo to include any Friday where the moon’s illumination met or exceeded 99.5%.

With this new cutoff I found the 3 more occurrences of the spookiest day of the year

Check out the full write up here:
http://davidameneyro.com/posts/20201018-friday-thirteenth-v1.html

cc: @WolframResearch

And if you liked this thread, check out my article on Perception & Analysis using Cellular Automata

http://davidameneyro.com/posts/20200411-Perception-and-Analysis-v1.html