Count the days of a given month and year

count-days.js

// determine how many days are in a given month 
// http://stackoverflow.com/questions/315760/what-is-the-best-way-to-determine-the-number-of-days-in-a-month-with-javascript
function daysInMonth( m, y ) {
    return m === 2 ? y & 3 || !( y % 25 ) && y & 15 ? 28 : 29 : 30 + ( m+ ( m >> 3 ) & 1 );
}

// determine the day number since beginning of the year
// http://stackoverflow.com/questions/8619879/javascript-calculate-the-day-of-the-year-1-366/27790471#27790471
function dayNo( y, m, d ){
    return --m * 31 - ( m > 1 ? ( 1054267675 >> m * 3 -6 & 7 ) - ( y & 3 || !( y % 25 ) && y & 15 ? 0 : 1 ) : 0 ) + d;
}