circa 1980 Casio with clock, similar to fx-8100

[ijabbott]

(12-12-2018 06:17 PM)grsbanks Wrote:  

(12-12-2018 11:24 AM)xerxes Wrote:  In such a case, I use the workaround of year-28 to have the correct weekday.

NB: that trick doesn't work unless every year in the interval that's a multiple of 4 is a leap year.

The latest turn of the century was 2000, which was a leap year (multiple of 400) but 1900 was not and 2100 won't be!

You could always go back to current year minus 400, except the calculator probably wouldn't like that either! (There are exactly 20871 weeks in 400 years of the Gregorian calendar, so the sequence of leap years and day of week that January 1 falls on repeats every 400 years.)