I had a Casio calculator that could show calendars like this. It could also play do-re-mi when you pressed digits and you could set an alarm with a jolly tune.

I had a Casio calculator that could show calendars like this. It could also play do-re-mi when you pressed digits and you could set an alarm with a jolly tune. And when I pressed the square root key repeatedly, the number got smaller and smaller until it showed 1. This was the 80s and it was my most precious thing.