Here's a full-year perpetual calendar cup. Just one moving part, and you adjust it just once a year. All the months end properly at 30 or 31 days (except February). You can really plan ahead with this device!
Watch the video!
A method for finding the day of the week for any date -- in your head.
Here's a full-year perpetual calendar cup. Just one moving part, and you adjust it just once a year. All the months end properly at 30 or 31 days (except February). You can really plan ahead with this device!
Watch the video!
Features of the cup: