This package implements the algorithm for determining the day of the week for any date.
The algorithm is was devised by the mathematician John Conway to be calculated mentally.
It's easy and uses remainders of 7 (because we only care about the weekday) to make big numbers small.
There is a command line training program. You can run it with swift run or:
swift build
.build/debug/doomsday --help
# you can copy the binary to your $PATH
cp -f .build/debug/doomsday ~/.local/bin/
doomsdayHere is how the the REPL looks:
By typing more ? you will get more detailed explanation:
Don't worry if that explanation seems too complicated! You will rarely need to calculate the anchors for year and century, so only the last easy step is necessary.