Error "...expects parameter 1 to be DateTime..." when saving or updating events.

Whenever saving or updating an event, I get this block of errors:

warning: date_timezone_set() expects parameter 1 to be DateTime, null given in /var/www/people/sites/all/modules/date/date_api_ical.inc on line 568.
warning: date_format() expects parameter 1 to be DateTime, null given in /var/www/people/sites/all/modules/date/date_api_ical.inc on line 654.
warning: date_timezone_set() expects parameter 1 to be DateTime, null given in /var/www/people/sites/all/modules/date/date_api_ical.inc on line 568.
warning: date_format() expects parameter 1 to be DateTime, null given in /var/www/people/sites/all/modules/date/date_api_ical.inc on line 654.

Here's the export of the field:

$content['fields']  = array (
  0 => 
  array (
    'label' => 'Date',
    'field_name' => 'field_date',
    'type' => 'datetime',
    'widget_type' => 'date_popup_repeat',
    'change' => 'Change basic information',
    'weight' => '-4',
    'default_value' => 'now',
    'default_value2' => 'strtotime',
    'default_value_code' => '',
    'default_value_code2' => '+ 1 hour',
    'input_format' => 'Y-m-d H:i:s',
    'input_format_custom' => 'Y-m-d H:i:s',
    'year_range' => '0:+1',
    'increment' => '15',
    'advanced' => 
    array (
      'label_position' => 'above',
      'text_parts' => 
      array (
        'year' => 0,
        'month' => 0,
        'day' => 0,
        'hour' => 0,
        'minute' => 0,
        'second' => 0,
      ),
    ),
    'label_position' => 'above',
    'text_parts' => 
    array (
    ),
    'description' => '',
    'group' => false,
    'required' => 1,
    'multiple' => 1,
    'repeat' => 1,
    'todate' => 'optional',
    'granularity' => 
    array (
      'year' => 'year',
      'month' => 'month',
      'day' => 'day',
      'hour' => 'hour',
      'minute' => 'minute',
    ),
    'default_format' => 'long',
    'tz_handling' => 'site',
    'timezone_db' => 'UTC',
    'repeat_collapsed' => '1',
    'op' => 'Save field settings',
    'module' => 'date',
    'widget_module' => 'date',
    'columns' => 
    array (
      'value' => 
      array (
        'type' => 'datetime',
        'not null' => false,
        'sortable' => true,
        'views' => true,
      ),
      'value2' => 
      array (
        'type' => 'datetime',
        'not null' => false,
        'sortable' => true,
        'views' => false,
      ),
      'rrule' => 
      array (
        'type' => 'text',
        'not null' => false,
        'sortable' => false,
        'views' => false,
      ),
    ),
    'display_settings' => 
    array (
      'label' => 
      array (
        'format' => 'above',
        'exclude' => 0,
      ),
      'teaser' => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
      'full' => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
      4 => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
      2 => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
      3 => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
      'token' => 
      array (
        'format' => 'default',
        'exclude' => 0,
      ),
    ),
  ),
);

This has been happening in all recent dev Date modules since at least the Mar25th dev release.