My mother has a pen with this feature (printed eternal calendar inside a rotatable sleeve) in the 1960s. It lasted many years. Good to know someone has finally invented it.
We had a giant plastic wall hanging perpetual calendar in the 1980s.
"Ring-A-Date Perpetual Calendar" I guess as a kid I got used to the grid of days not always starting in the same place.
Yep, that was the pen (minus the corporate logo). I guarantee it was endless minutes of fascination to a child fascinated by things that do thought work. Don't get me started on her slide rule.
