About understanding, we're used to it but you can't trivially know whether 02/05/2026 is a Monday. Even remembering whether July has 30 or 31 days can be a chore. Irregular months also can have some small annoying effects since "in a month" is not always the same amount of days. There's even the 360 day calendar for that https://en.wikipedia.org/wiki/360-day_calendar
Actually there are trivially easy ways to calculate DOW off the top of your head. No one bothers because it was never a real problem. People used to carry their calendar books on them to keep track of their engagements. Now we carry a smartphone.
Nevertheless, my colleague bothered to do it and he could tell you the DOW without pausing. He is of average intelligence maybe a little more intelligent than I (though I was better at mental math)
Nevertheless, my colleague bothered to do it and he could tell you the DOW without pausing. He is of average intelligence maybe a little more intelligent than I (though I was better at mental math)