code: function datePrettyFormat(ms, opts) {
    if (typeof ms !== 'number') {
      throw new TypeError('Expected a number');
    }
  
    if (ms < 1000) {
      return Math.ceil(ms) + 'ms';
    }
  
    opts = opts || {};
  
    var secDecimalDigits = typeof opts.secDecimalDigits === 'number' ? opts.secDecimalDigits : 1;
    var ret = [];
    var parsed = formatDate(ms);
  
    ret = add(ret, parsed.years, 'y');
    ret = add(ret, parsed.days, 'd');
    ret = add(ret, parsed.hours, 'h');
    ret = add(ret, parsed.minutes, 'm');
  
    if (opts.compact) {
      ret = add(ret, parsed.seconds, 's');
      return '~' + ret[0];
    }
  
    ret = add(ret, (ms / 1000 % 60).toFixed(secDecimalDigits).replace(/\.0$/, ''), 's');
  
    return ret.join(' ');
  }
docs: /*
  The datePrettyFormat function converts milliseconds to a human readible
  date output that corresponds to a specific format.