/**
* Returns the default last N number of dates to display for a given period.
*
* @param string $period 'day', 'week', 'month' or 'year'
* @return int
*/
public static function getDefaultLastN($period)
{
    switch ($period) {
        case 'week':
            return 26;
        case 'month':
            return 24;
        case 'year':
            return 5;
        case 'day':
        default:
            return 30;
    }
}