node-calendar.js
function leapdays(y1, y2) {
      y1--;
      y2--;
      return (Math.floor(y2/4) - Math.floor(y1/4)) - (Math.floor(y2/100) - Math.floor(y1/100)) + (Math.floor(y2/400) - Math.floor(y1/400));
    }
function leapdays(y1, y2) {
      y1--;
      y2--;
      return (Math.floor(y2/4) - Math.floor(y1/4)) - (Math.floor(y2/100) - Math.floor(y1/100)) + (Math.floor(y2/400) - Math.floor(y1/400));
    }
function leapdays ( y1 , y2 ) { y1 -- ; y2 -- ; return ( Math . floor ( y2 / 4 ) - Math . floor ( y1 / 4 ) ) - ( Math . floor ( y2 / 100 ) - Math . floor ( y1 / 100 ) ) + ( Math . floor ( y2 / 400 ) - Math . floor ( y1 / 400 ) ) ; }
Return number of leap years in range [y1, y2).
Assumes y1 <= y2.

@param {Number} y1
@param {Number} y2
@api public
Return number of leap years in range [ y1 y2 ) . Assumes y1 < = y2 .