Psychic thinking, technically of course

I can’t speak about what I do in office. (ok, not yet). But I need to write something. So here goes:     A “small” algo to retrieve number of days in a month. Don’t ask me it s efficiency (modulus is never fast , an alternative would be something similar to isInt function ):     /// January = 1, February = 2 and so on. /// year will be used only if month = 2 function daysInTheMonth(var monthNumber, var yearNumber) {                 // if February, and year is divisible by 4 but not divisible by 100, return 28. Else return 28.                 // since years which are divisible by 100 should not be leap years                 if(monthNumber == 2)  { return (yearNumber%4 ==0 && yearNumber%100>0)? 29 : 28  }                 return (monthNumber > 7) ?  ((monthNumber%2 ==0) ? 30 : 31) : ((monthNumber%2 ==0) ? 31: 30);   // another option // if(monthNumber > 7) monthNumber++; // return ((monthNumber%2 ==0) ? 30 : 31)     }