Originally, it does. But I renamed it to de.php, so in this case it does not exist.
But default_locale is set to en_US, so this error message is not anymore important.
I have copied the whole error message from the html code:
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.NUMBEROFEVENTS,Number of events to display on default view.)
line 98 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.DEFAULTDATEHEADER,Default date header (displays when no date range has been selected))
line 99 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.NUMBERFUTUREDATES,Number of future dates to show for repeating events)
line 100 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.TITLE,Title)
line 109 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.STARTDATE,Start Date)
line 110 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.STARTTIME,Start Time)
line 111 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
ERROR:Error 512: i18n::include_by_class: Class EVENTCALENDAR not found
At l1259 in C:\xampp\htdocs\sapphire\core\i18n.php
user_error(i18n::include_by_class: Class EVENTCALENDAR not found,512)
line 1259 of i18n.php
i18n::include_by_class(EVENTCALENDAR)
line 132 of Core.php
_t(EVENTCALENDAR.ENDTIME,End Time)
line 112 of Calendar.php
Calendar->getCMSFields(CMSMain)
line 363 of CMSMain.php
CMSMain->getEditForm(46)
line 752 of LeftAndMain.php
LeftAndMain->EditForm()
line 227 of LeftAndMain.php
LeftAndMain->getitem(Array)
line 261 of Controller.php
Controller->run(Array)
line 104 of Director.php
Director::direct(/admin/getitem)
line 158 of main.php
<p id="Form_EditForm_error" class="message " style="display: none"></p>
<fieldset>
<ul class="tabstrip">
<li class="first "><a href="#Root_Content_set" id="tab-Root_Content_set">Content</a></li>
<li class=" middle"><a href="#Root_Behaviour" id="tab-Root_Behaviour">Behaviour</a></li>
<li class=" middle"><a href="#Root_Todo" id="tab-Root_Todo">To-do</a></li>
<li class=" middle"><a href="#Root_Reports_set" id="tab-Root_Reports_set">Reports</a></li>
<li class="last "><a href="#Root_Access" id="tab-Root_Access">Access</a></li>
</ul>
<div class="tab" id="Root_Content_set">
<ul class="tabstrip">
<li class="first "><a href="#Root_Content_set_Main" id="tab-Root_Content_set_Main">Main</a></li>
<li class=" middle"><a href="#Root_Content_set_Metadata" id="tab-Root_Content_set_Metadata">Meta-data</a></li>
<li class=" middle"><a href="#Root_Content_set_Configuration" id="tab-Root_Content_set_Configuration">Configuration</a></li>
<li class="last "><a href="#Root_Content_set_Announcements" id="tab-Root_Content_set_Announcements">Announcements</a></li>
</ul>
<div class="tab" id="Root_Content_set_Main">
<div id="Title" class="field text "><label class="left" for="Form_EditForm_Title">Page name</label><span class="middleColumn"><input class="text" type="text" id="Form_EditForm_Title" name="Title" value="New Calendar" ></span></div>
<div id="MenuTitle" class="field text "><label class="left" for="Form_EditForm_MenuTitle">Navigation label</label><span class="middleColumn"><input class="text" type="text" id="Form_EditForm_MenuTitle" name="MenuTitle" value="New Calendar" ></span></div>
<div id="Content" class="field htmleditor "><label class="left" for="Form_EditForm_Content">Content</label><span class="middleColumn"><textarea class="htmleditor typography" rows="15" cols="20" style="width: 97%; height: 240px" tinymce="true" id="Form_EditForm_Content" name="Content"></textarea></span></div>
</div>
<div class="tab" id="Root_Content_set_Metadata">
<div id="URL" class="field fieldgroup "><label class="left" for="Form_EditForm_">URL</label><span class="middleColumn"><span class="fieldgroup"><label>http://www.yoursite.com/</label> <input class="UniqueRestrictedTextField" type="text" id="Form_EditForm_URLSegment" name="URLSegment" value="new-calendar" size="30" ><input type="hidden" name="restricted-messages[Form_EditForm_URLSegment]" id="Form_EditForm_URLSegment-restricted-message" value="Another page is using that URL. URL must be unique for each page" ><input type="hidden" name="restricted-chars[Form_EditForm_URLSegment]" id="Form_EditForm_URLSegment-restricted-chars" value="[^A-Za-z0-9-]+" ><input type="hidden" name="restricted-chars[Form_EditForm_URLSegment]" id="Form_EditForm_URLSegment-restricted-chars-replace" value="-" ><input type="hidden" name="restricted-chars[Form_EditForm_URLSegment]" id="Form_EditForm_URLSegment-restricted-chars-message" value="URLs can only be made up of letters, digits and hyphens." > <label>/</label> </span></span></div>
<h2>Search Engine Meta-tags</h2>
<div id="MetaTitle" class="field text "><label class="left" for="Form_EditForm_MetaTitle">Title</label><span class="middleColumn"><input class="text" type="text" id="Form_EditForm_MetaTitle" name="MetaTitle" value="" ></span></div>
<div id="MetaDescription" class="field textarea "><label class="left" for="Form_EditForm_MetaDescription">Description</label><span class="middleColumn"><textarea id="Form_EditForm_MetaDescription" name="MetaDescription" rows="5" cols="20"></textarea></span></div>
<div id="MetaKeywords" class="field textarea "><label class="left" for="Form_EditForm_MetaKeywords">Keywords</label><span class="middleColumn"><textarea id="Form_EditForm_MetaKeywords" name="MetaKeywords" rows="5" cols="20"></textarea></span></div>
<div id="AdvancedOptions" class=" toggleCompositeField startClosed">
<h2 style="cursor: pointer;" class="trigger">
<img class="triggerClosed" src="sapphire/images/toggle-closed.gif" alt="+" style="display:none;" title="Show" >
<img class="triggerOpened" src="sapphire/images/toggle-open.gif" alt="-" style="display:none;" title="Hide" >
Advanced Options...
</h2>
<div class="contentMore">
<div id="ExtraMeta" class="field textarea "><label class="left" for="Form_EditForm_ExtraMeta">Custom Meta Tags</label><span class="middleColumn"><textarea id="Form_EditForm_ExtraMeta" name="ExtraMeta" rows="5" cols="20"></textarea></span></div>
<p>Manually specify a Google Sitemaps priority for this page (<a href="https://www.google.com/webmasters/tools/docs/en/protocol.html#prioritydef">?</a>)</p>
<div id="Priority" class="field dropdown "><label class="left" for="Form_EditForm_Priority">Page Priority</label><span class="middleColumn"><select name="Priority" id="Form_EditForm_Priority"><option value="0.0">Not indexed</option><option selected="selected" value="1.0">1 - Most important</option><option value="0.9">2</option><option value="0.8">3</option><option value="0.7">4</option><option value="0.6">5</option><option value="0.5">6</option><option value="0.4">7</