Gauss's Weekday Algorithm, Visualized(lukasmetzner.github.io)
lukasmetzner.github.io
Gauss's Weekday Algorithm, Visualized
https://lukasmetzner.github.io/blog/gauss-weekday.html
8 comments
This is simply the fact that 365 % 7 == 1, with leap year adjustments.
That's correct, but it's pretty well-hidden because at first sight there is no term that's just the year modulo 7. That's because a Gregorian calendar cycle of 400 years is coincidentally an integer amount of weeks long, so after the term modulo 400 you don't need another correction anymore.
To recover the fact that 365 % 7 == 1 from the given formula, one can notice that the sum of the coefficients 5+4+6=15, which modulo 7 is 1.
To recover the fact that 365 % 7 == 1 from the given formula, one can notice that the sum of the coefficients 5+4+6=15, which modulo 7 is 1.
I guess the leap year adjustment is the tricky part
With this plus the Doomsday algorithm, I am invincible.
For people who don’t know, John H. Conway’s doomsday algorithm allows you to compute the day of the week for any date by starting from a set of memorable dates (called “doomsdays”) and working from there. https://en.wikipedia.org/wiki/Doomsday_rule
So for example doomsday for this year is a Saturday, so I know the last day in February is a Saturday (this Saturday in fact) and also that Independence Day, Boxing Day and Halloween are also going to be on Saturday this year, because they are all Doomsdays (on non-leap years).
So for example doomsday for this year is a Saturday, so I know the last day in February is a Saturday (this Saturday in fact) and also that Independence Day, Boxing Day and Halloween are also going to be on Saturday this year, because they are all Doomsdays (on non-leap years).
as Easter is nearing the Gaussian compute algorithm deserves some attention,too