After full convert DB from 3.0.12 cannot enter to Admin Panel, HTTP 500 Internal Server Error.
Here is the log of PHP:

PHP Fatal error: Uncaught exception 'Exception' with message 'DateTime::__construct(): Failed to parse time string (@) at position 0 (@): Unexpected character' in C:\Inetpub\phpBB3.asc\phpbb\datetime.php:50
Stack trace:
#0 C:\Inetpub\phpBB3.asc\phpbb\datetime.php(50): DateTime->__construct('@', Object(DateTimeZone))
#1 C:\Inetpub\phpBB3.asc\phpbb\user.php(713): phpbb\datetime->__construct(Object(phpbb\user), '@', Object(DateTimeZone))
#2 C:\Inetpub\phpBB3.asc\includes\acp\acp_main.php(586): phpbb\user->format_date(NULL)
#3 C:\Inetpub\phpBB3.asc\includes\functions_module.php(652): acp_main->main('main', 'main')
#4 C:\Inetpub\phpBB3.asc\adm\index.php(81): p_master->load_active()
#5

thrown in C:\Inetpub\phpBB3.asc\phpbb\datetime.php on line 50