index.js

function createHandler(divisor,noun,restOfString){
	return function(diff){
		var n = Math.floor(diff/divisor);
		var pluralizedNoun = noun + ( n > 1 ? 's' : '' );
		return "" + n + " " + pluralizedNoun + " " + restOfString;
	}
}

var formatters = [
	{ threshold: -31535999, handler: createHandler(-31536000,	"year",     "from now" ) },
	{ threshold: -2591999, 	handler: createHandler(-2592000,  	"month",    "from now" ) },
	{ threshold: -604799,  	handler: createHandler(-604800,   	"week",     "from now" ) },
	{ threshold: -172799,   handler: createHandler(-86400,    	"day",      "from now" ) },
	{ threshold: -86399,   	handler: function(){ return      	"tomorrow" } },
	{ threshold: -3599,    	handler: createHandler(-3600,     	"hour",     "from now" ) },
	{ threshold: -59,     	handler: createHandler(-60,       	"minute",   "from now" ) },
	{ threshold: -0.9999,   handler: createHandler(-1,			"second",   "from now" ) },
	{ threshold: 1,        	handler: function(){ return      	"just now" } },
	{ threshold: 60,       	handler: createHandler(1,        	"second",	"ago" ) },
	{ threshold: 3600,     	handler: createHandler(60,       	"minute",	"ago" ) },
	{ threshold: 86400,    	handler: createHandler(3600,     	"hour",     "ago" ) },
	{ threshold: 172800,   	handler: function(){ return      	"yesterday" } },
	{ threshold: 604800,   	handler: createHandler(86400,    	"day",      "ago" ) },
	{ threshold: 2592000,  	handler: createHandler(604800,   	"week",     "ago" ) },
	{ threshold: 31536000, 	handler: createHandler(2592000,  	"month",    "ago" ) },
	{ threshold: Infinity, 	handler: createHandler(31536000, 	"year",     "ago" ) }
];

var prettydate = {
	format: function (date) {
		var diff = (((new Date()).getTime() - date.getTime()) / 1000);
		for( var i=0; i<formatters.length; i++ ){
			if( diff < formatters[i].threshold ){
				return formatters[i].handler(diff);
			}
		}
		throw new Error("exhausted all formatter options, none found"); //should never be reached
	}
}

// for nodejs env
if (typeof module !== 'undefined'){
	module.exports = prettydate;
}

// for meteor env
PrettyDate = prettydate;