The RSS feed for COM_FINDER search throw an Error 500 for all feed type.
(This is an error i had already logged here : https://developer.joomla.org/joomlacode-archive/issue-30167.html)

Steps to reproduce the issue

1 - Set $offset value of configuration.php :

public $offset = 'Europe/Paris';
public $offset_user = 'UTC';

2 - Languages published in the website are : French (default), English.

3 - Set a "menu item alias" for com_finder and name it "search" :

4 - Try to access URL like the example below :
www.mywebsite.com/search?q=Mac&format=feed&type=rss

Expected result

Display of an Atom or RSS feed related to your search term.
This should also work if you have search feed for tags enabled.

Actual result

Error displaying the error page:
Unable to load renderer class: DateTime::__construct():
Failed to parse time string (jeudi 26 décembre 2013) at position 0 (j):
The timezone could not be found in the database

Note : 'jeudi 26 décembre 2013' is the date submitted in French.
English equivalent of : 'Thursday 26 December 2013'

System information (as much as possible)

Joomla version is : 3.5.1

PHP version is : 5.6

In language File for French (fr-FR.ini) you have the values set as below :
(the joomla original value is commented by ";")

; DATE_FORMAT_LC="l j F Y"
DATE_FORMAT_LC="j-m-Y"
; DATE_FORMAT_LC1="l j F Y"
DATE_FORMAT_LC1="j-m-Y"
; DATE_FORMAT_LC2="l j F Y H:i"
DATE_FORMAT_LC2="j-m-Y H:i"
; DATE_FORMAT_LC3="j F Y"
DATE_FORMAT_LC3="j-m-Y"
DATE_FORMAT_LC4="j/m/Y"
DATE_FORMAT_JS1="j/m/y"

Proposal of Solution

The reason of the issue (in my opinion) lies in file <joomla_path>/components/com_finder/views/search/view.feed.php
at line 87. We have a date formated as : JHtml::date($result->start_date, 'l d F Y').
If $result->start_date value does not match format 'l d F Y', the JHtml::date fails.

Given that in feed.php found in <joomla_path>/libraries/joomla/document/feed/feed.php
the type of feeditem date can only be RFC 822, ISO 8601 or Unix Timestamp :

Extract from feed.php :
/**
* Published date
*
* optional
*
* May be in one of the following formats:
*
* RFC 822:
* "Mon, 20 Jan 03 18:05:41 +0400"
* "20 Jan 03 18:05:41 +0000"
*
* ISO 8601:
* "2003-01-20T18:05:41+04:00"
*
* Unix:
* 1043082341
*
* @var string
* @SInCE 11.1
*/

I propose to always set date format as Unix timestamp to stay safe :

To fix this issue, in statement at line 87 from file <joomla_path>/components/com_finder/views/search/view.feed.php, replace the "l d F Y" by "U":

Before :
$item->date = intval($result->start_date) ? JHtml::date($result->start_date, '"l d F Y') : $result->indexdate;

After :
$item->date = intval($result->start_date) ? JHtml::date($result->start_date, 'U') : $result->indexdate;

What do you think ?

Attached is my version of : view.feed.php (renamed as view.feed.php.txt to be allowed for upload)
view.feed.php.txt
And this works on my website : www.anikijournal.com
Example : http://www.anikijournal.com/search?q=OTA&format=feed&type=atom