I learned Trig and Calculus with no calculator. When I entered college the math professor saw me using the pi chart to do the work. Before I took the test I did a circle and broke it down. My HS teacher taught us how to use it as we remembered the fractions and numeric number attached to it.Umm, I remember my math teachers and older folks like my parents refusing to let us use calculators for schoolwork cuz, "You won't always have a calculator with you".
How'd that prediction work out?
That same calculator device we all carry in our pockets always comes stock with a calendar.
Never cared for learning much math but love math theory.
Never cared enough to learn the 30/31 day thing, never found any value in knowing it.
I do absolutely know this, however, "Android loves me, this I know, cuz my Samsung devices tell me so".
I got a 100. She called me to her office. She said I didn't belong in the class if I could do that math without a calculator. She did the paperwork for me to skip two classes and get credit for it.
In computer class, I saw everyone take out their calculator for the first test. It was allowed. I did it by hand, got 100. The instructor was impressed, especially since some with calculators did badly.
#MathandScienceNerd.