Roundcube blank page / error 500

Hello,
like a thunderclap in a clear sky, this morning roundcube page it's blank with the error 500.
But not for all domains: some of those works normally.
In /var/www/html/roundcubemail-1.2.3/logs/errors I see:
thrown in /var/www/html/roundcubemail-1.2.3/program/lib/Roundcube/rcube_user.php on line 523
[15-Dec-2016 11:49:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:49:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:50:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:50:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:50:17 UTC] PHP Warning: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those me$
[15-Dec-2016 11:51:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:51:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:52:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:52:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:53:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:53:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:54:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:54:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:55:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:55:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:55:17 UTC] PHP Warning: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those me$
[15-Dec-2016 11:56:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$
[15-Dec-2016 11:56:17 UTC] PHP Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of tho$

I search in google and I put date_default_timezone_set('Europe/Rome'); at beginning of every php.ini a Ihave in my server; reboot; nothing, same error.

What could be the problem?
Why some domains works normally?
Thank you very much

Hi,

What do you see in the domain/general apache log when accessing roundcube?

and I put date_default_timezone_set('Europe/Rome');

Click to expand...

That's not the correct format.

The date.timezone line is already present in your php.ini and looks like:

Remove your own line, then look for the line I just posted in your php.ini and change it to:
Save it and restart httpd, then it should be correct.

ViAdCk: what log exaclty you mean? /var/log/httpd/domains/mydomain.xx.log? .error.log?

Richard G: I followed you hint and restarted apache, but I have the same error: some domains work correctly and some others no.

Yes indeed, if you access at domain/roundcube it should give some insight.

I reboot the server due a mysql problem and now everything works fine...