[SOLVED] Changing format for date is not accepted

Other query to run:

SELECT COLLATION_NAME, COUNT(*) AS total
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = 'your_database_name'
AND LOWER(TABLE_NAME) LIKE '%jem%'
AND COLLATION_NAME IS NOT NULL
GROUP BY COLLATION_NAME;

Send me the result.

I think that I have found the error in JEM 4.2.1.
The update script forces collation on some tables.

The installation error was caused by a collation mismatch during the JEM database update.

Some Joomla/MySQL 8 installations use utf8mb4_0900_ai_ci as the database collation, while JEM was explicitly creating or converting some tables with utf8mb4_unicode_ci. When MySQL compared text columns using different collations during the update, it stopped with an "Illegal mix of collations" error.

This has been fixed in the JEM SQL installer/update scripts. JEM will no longer force utf8mb4_unicode_ci; new JEM tables will inherit the charset and collation from the Joomla database.

The fix will be included in the next RC4 refresh package on GitHub.
Thanks for reporting it.

New RC4 zip file update [02.07.2026 16:30] with the fix

Updating from joomla 5.4.6 and jem 4.4.2 to to new 4.5.0 rc4 at 2026-07-02 1800 provides NO error message -> successful installation. 
Database structure is without errors. The update check now show a nice new panel with installed release 4.50 rc4

I can edit events. 

But I can not change any parameter in the JEM settings. For instance Event Page - changing from structured details to compact details  - then save refreshes the screen and shows the previous value again. 

Really strange. Where are the xml option stored - in database or in plain xml files? Where? 
 

Checking the apache2 error log file: 

For each time I tried to save the settings there is a message: 
PHP Warning: PHP Request Startup: Input variables exceeded 1000. To increase the limit change max input vars in php. ini .......

 

... and after changing "max_input_vars" to 2000 in the php.ini in the right version directory 8.4 and also removing the ; in front then after restart the issues is solved (for me).