gistfile1.js

var countNumberActiveUsersInRangeXDaysAgo = function (range_length_in_days, numDaysAgo_start) {

	var deferred = Q.defer();

	var startDate = new Date();
	startDate.setDate(startDate.getDate() - numDaysAgo_start);
	var s = ObjectID.createFromTime(startDate.getSeconds());

	var endDate = new Date();
	endDate.setDate(endDate.getDate() - numDaysAgo_start + range_length_in_days);
	var e = ObjectID.createFromTime(endDate.getSeconds());		// should i use seconds since 1970???

	console.log('seconds = '+endDate.getSeconds());

	var conditions = { _id: {$gte: s, $lt:e}};

	console.log('conditions='+JSON.stringify(conditions));

	User.count(conditions, function(err, count) {
		if ( err ) {
			deferred.reject(err);
		} else {
			deferred.resolve(count);
		}
	});
	return deferred.promise;
};