TYPO3 Core

I can confirm this bug still exists in TYPO3 8.7.12

The reason behind this is a wrong concatenation of JavaScript values in Line 468 in File typo3/sysext/frontend/Classes/View/AdminPanelView.php

 $output[] = '  <input type="text" id="preview_simulateDate" name="TSFE_ADMIN_PANEL[preview_simulateDate]_hr" onchange="TSFEtypo3FormFieldGet(' . GeneralUtility::quoteJSvalue('TSFE_ADMIN_PANEL[preview_simulateDate]') . ', "datetime", "", 1,0);" />';

This code leads to wrong JavaScript code in the Admin Panel (see the mixed up quotes for call to TSFEtypo3FormFieldGet ) and a JavaScript error in onChange:

<div class="typo3-adminPanel-form-group">  
<label for="preview_simulateDate">    Simulate time  </label>  
<input type="text" id="preview_simulateDate" name="TSFE_ADMIN_PANEL[preview_simulateDate]_hr" 
onchange="TSFEtypo3FormFieldGet('TSFE_ADMIN_PANEL[preview_simulateDate]', "datetime", "", 1,0);" />  
<input type="hidden" name="TSFE_ADMIN_PANEL[preview_simulateDate]" value="1522195200" />
</div>

The corrected code should read either

// remove obsolete call to GeneralUtility::quoteJSvalue
 $output[] = '  <input type="text" id="preview_simulateDate" name="TSFE_ADMIN_PANEL[preview_simulateDate]_hr" 
 onchange="TSFEtypo3FormFieldGet(\'TSFE_ADMIN_PANEL[preview_simulateDate]\', \'datetime\', \'\', 1,0);" />';

or

// keep call to GeneralUtility::quoteJSvalue but fix the remaining quotes for TSFEtypo3FormFieldGet
 $output[] = '  <input type="text" id="preview_simulateDate" name="TSFE_ADMIN_PANEL[preview_simulateDate]_hr" 
 onchange="TSFEtypo3FormFieldGet(' . GeneralUtility::quoteJSvalue('TSFE_ADMIN_PANEL[preview_simulateDate]') . ', \'datetime\', \'\', 1,0);" />';

Patch set 1 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56461

Applied in changeset 787fbedbcb0f2c5ca652b8c7e4c2a122683a0be5.