from-now.coffee

fromNow = (d) ->
	unless d instanceof Date
		d = new Date(d)

	difference = d - new Date()

	# string, limit, divider
	limits = [
		["momentos",    1000,                  1]
		["%d segundos", 1000*60,               1000]
		["um minuto",   1000*60*2,             1000*60]
		["%d minutos",  1000*60*60,            1000*60]
		["uma hora",    1000*60*60*2,          1000*60*60]
		["%d horas",    1000*60*60*24,         1000*60*60]
		["um dia",      1000*60*60*24*2,       1000*60*60*24]
		["%d dias",     1000*60*60*24*30,      1000*60*60*24]
		["um mês",      1000*60*60*24*30*2,    1000*60*60*24*30]
		["%d meses",    1000*60*60*24*30*12,   1000*60*60*24*30]
		["um ano",      1000*60*60*24*30*12*2, 1000*60*60*24*30*12]
		["%d anos",     Infinity,              1000*60*60*24*30*12]
	]

	# past or future
	# tiny tolerance to permit for `fromNow(new Date())` to be in the past
	str = if difference <= 5 then 'há %s' else 'em %s'

	difference = Math.abs(difference)

	limit = do (difference) ->
		for limit in limits
			if difference < limit[1]
				return limit

	return str.replace('%s', limit[0].replace('%d', (difference/limit[2]).toFixed(0)))

from-now.js

fromNow = function(d) {

  var difference, limit, limits, str;

  if (!(d instanceof Date)) {
    d = new Date(d);
  }

  difference = d - new Date();

  // string, limit, divider
  limits = [
        ["momentos",    1000,                  1],
        ["%d segundos", 1000*60,               1000],
        ["um minuto",   1000*60*2,             1000*60],
        ["%d minutos",  1000*60*60,            1000*60],
        ["uma hora",    1000*60*60*2,          1000*60*60],
        ["%d horas",    1000*60*60*24,         1000*60*60],
        ["um dia",      1000*60*60*24*2,       1000*60*60*24],
        ["%d dias",     1000*60*60*24*30,      1000*60*60*24],
        ["um mês",      1000*60*60*24*30*2,    1000*60*60*24*30],
        ["%d meses",    1000*60*60*24*30*12,   1000*60*60*24*30],
        ["um ano",      1000*60*60*24*30*12*2, 1000*60*60*24*30*12],
        ["%d anos",     Infinity,              1000*60*60*24*30*12]
  ];

  str = difference <= 5 ? 'há %s' : 'em %s';
  difference = Math.abs(difference);

  limit = (function(difference) {
    var _i, _len;
    for (_i = 0, _len = limits.length; _i < _len; _i++) {
      limit = limits[_i];
      if (difference < limit[1]) {
        return limit;
      }
    }
  })(difference);

  return str.replace('%s', limit[0].replace('%d', (difference / limit[2]).toFixed(0)));
};

Beautiful usage of do :)