How many calendars are there?

Humble Pi on Maths Gear: https://mathsgear.co.uk/products/humble-pi

Get your free gift when you pre-order!
https://www.penguin.co.uk/articles/2018/nov/humble-pi-preorder.html

Here it is on Amazon.
https://www.amazon.co.uk/Humble-Pi-Comedy-Maths-Errors/dp/0241360234/ref=sr_1_1?_encoding=UTF8&tag=stanupmath-21

And Waterstones why not!
https://www.waterstones.com/book/humble-pi/matt-parker/9780241360231

Right, now on to details about the actual video.

All the photos of retro calculators are from this great website: My Calc DB
http://mycalcdb.free.fr/main.php?l=0&p=1

I do not have permission to use the images for anything other than my own personal use. So no, I cannot sell you a copy of "Calculators of 1974". I'm sorry. Because it's amazing.

823 years on Snopes.
https://www.snopes.com/fact-check/money-bags/
CORRECTIONS
- At 7:38 I say “400 days” when I mean “400 years”. First spotted by Jim Fortune.
- User "SmackleFunky" spotted a typo in the above correction. Does that count as a video correction? I'm not sure.
- I said 13 days when talking about England's calendar reform of 1752 when they actually skipped 11 days. Sorry! Wednesday 2 September was followed by Thursday 14 September. Spotted by macronencer.
- Yes, I had “refor” above instead of “reform”. Another meta-correction!
- Let me know if you spot anything else. Preferably in the video and not the corrections.
Thanks to my Patreon supports who do support these videos and make them possible. Here is a random subset:

Claire Greenhalgh
Ben White
Willy Marple
Sjoerd Wennekes
Quinten Palmer

Support my channel and I can make more maths videos with a better camera that can hold focus and contrast levels.
https://www.patreon.com/standupmaths
Music by Howard Carter
Filming and editing by Matt Parker
Design by Simon Wright
MATT PARKER: Stand-up Mathematician
Website: http://standupmaths.com/
Maths book: http://makeanddo4D.com/
Nerdy maths toys: http://mathsgear.co.uk/
Nerdy maths toys: http://mathsgear.co.uk/

Видео How many calendars are there? канала Stand-up Maths