var cron = require('cron'), sys = require('sys');
new cron.CronJob('* * * * * *', function(){
    sys.puts('You will see this message every second');
});

Asterisk. E.g. *
Ranges. E.g. 1-3,5
Steps. E.g. */2

var cron = require('cron'), sys = require('sys');
new CronJob('00 30 11 * * 2-6', function(){
    // Runs every weekday (Monday through Friday)
    // at 11:30:00 AM. It does not run on Saturday
    // or Sunday.
});

	try {
		new cron.CronTime('invalid cron pattern', function() {
			sys.puts('this should not be printed');
		})
	} catch(ex) {
		sys.puts("cron pattern not valid");
	}

From source: `sudo npm install`
From npm: `sudo npm install cron`