/**

* Determines the day of the week using Tomohiko Sakamoto's Algorithm

* to calculate Day of Week based on Gregorian calendar.

*/

function dow(y, m, d) {

let t = [0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4];

y -= (m < 3) ? 1 : 0;

return Math.round(y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;

}

/**

* Determines the day of the week using Tomohiko Sakamoto's Algorithm

* to calculate Day of Week based on Gregorian calendar.

*/

function dowS(y, m, d) {

switch (dow(y, m, d)) {

case 0:

return "Sunday";

case 1:

return "Monday";

case 2:

return "Tuesday";

case 3:

return "Wednesday";

case 4:

return "Thursday";

case 5:

return "Friday";

case 6:

return "Saturday";

default:

console.log("Unknown dow");

}

return null;

}

module.exports = { dow, dowS};