using some dates as contextual filters in drupal views generating php warnings

With CiviCRM 4.3.5, Drupal 7.22 and Views 7.x-3.7 and creating a CiviCRM Events view in Drupal with a Contextual filter of Start Date Month (for example) I get the following warnings:

Warning: timezone_open(): Unknown or bad timezone (0) in format_date() (line 1976 of ####/includes/common.inc).
Warning: date_timezone_set() expects parameter 2 to be DateTimeZone, boolean given in format_date() (line 2014 of ####/includes/common.inc).

Seems to be triggered by the calls to Drupal's format_date() function, Drupal is expecting NULL when using the default timezone and 0 is being interpreted as a timezone id

Is it safe to remove the last argument to those function calls? ie.
return format_date(strtotime("2005" . $month . "15"), 'custom', $this->format, 0);
becomes
return format_date(strtotime("2005" . $month . "15"), 'custom', $this->format);

civicrm files that are affected:
views_handler_argument_civicrm_month.inc
views_handler_argument_civicrm_day.inc

I'm getting a "Broken missing handler" when using the "full date" handler but I'll create another issue for that once I look into it further (and figure out if it's not just me).