human-readable-duraton-format.js

function formatDuration (seconds) {
  return [60, 3600, 86400, 31536000]
    .reduceRight(function (results, current) {
      var seconds = results.pop();
      results.push(Math.floor(seconds / current));
      results.push(seconds - results[results.length - 1] * current);
      return results;
    }, [seconds])
    .map(function (value, index) {
      var words = ['year', 'day', 'hour', 'minute', 'second'];
      return value ? value + ' ' + words[index] + (value == 1 ? '' : 's') : 0;
    })
    .filter(Boolean)
    .join(', ')
    .replace(/,([^,]*)$/, ' and$1') || 'now';
}

console.log(formatDuration(0));         // => now
console.log(formatDuration(60));        // => 1 minute
console.log(formatDuration(61));        // => 1 minute and 1 second
console.log(formatDuration(62));        // => 1 minute and 2 seconds
console.log(formatDuration(3662));      // => 1 hour, 1 minute and 2 seconds
console.log(formatDuration(366212345)); // => 11 years, 223 days, 13 hours, 39 minutes and 5 seconds