ZoneMinder is not installed properly: php's date.timezone is not set to a valid timezone

When visiting 'http://zoneminder.address/zm', the web browser shows:

ZoneMinder is not installed properly: php's date.timezone is not set to a valid timezone

Package: zoneminder 1.30.2-xenial1

Way to reproduce (just follow the install instructions step by step):

On a clean LXD container with Ubuntu 16.04.2
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add-apt-repository -y ppa:iconnor/zoneminder

apt-get update
apt-get -y upgrade
apt-get -y dist-upgrade

MYSQL_ROOT="Password"
echo mysql-server mysql-server/root_password select $MYSQL_ROOT | debconf-set-selections
echo mysql-server mysql-server/root_password_again select $MYSQL_ROOT | debconf-set-selections

apt-get -y install zoneminder

mysql -uroot -p$MYSQL_ROOT < /usr/share/zoneminder/db/zm_create.sql
mysql -uroot -p$MYSQL_ROOT -e "grant select,insert,update,delete,create,alter,index,lock tables on zm.* to 'zmuser'@localhost identified by 'zmpass';"

chmod 740 /etc/zm/zm.conf
chown root:www-data /etc/zm/zm.conf
chown -R www-data:www-data /usr/share/zoneminder/

a2enconf zoneminder
a2enmod cgi
a2enmod rewrite

sed -i 's|;date.timezone =|date-timezone = Europe/Berlin|' /etc/php/7.0/apache2/php.ini

systemctl reload apache2