function get_business_days (date_start, date_end)
{
	var bdays = 0;
	while (date_start <= date_end)
	{
		if (date_start.getDay () != 0 && date_start.getDay () != 6)
			bdays++; // increment business days (exclude weekend)
		date_start.setDate (date_start.getDate () + 1);
	}
	return bdays;
}