Please help us by providing the following info. Before posting please also check the pinned "Known issues" threads and make sure that you're running the latest available version for your oC release: https://owncloud.org/changelog/
Steps to reproduce
1. Upgrade to 8.2.10
2. Upgrade to 9.0.8
Calendar should work
Calendar does not work correctly, the page is displayed inside Owncloud but completely empty.
See screenshot here: http://imgur.com/a/YmDSC
WebDAV however keeps working without issues.
Operating system: Linux
Web server: Apache 2.4.10
Database: Mysql 5.5.53
PHP version: 5.6.30+dfsg-0+deb8u1
ownCloud version (see ownCloud admin page): 9.0.8
Updated from an older ownCloud or fresh install: update
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):
ownCloud log (data/owncloud.log)
Please paste possible errors in the following code block, see https://central.owncloud.org/t/how-to-find-webserver-or-oc-logfile-enable-php-logfile/808 for more info
Integrity status for oC9+
Integrity checker has been disabled. Integrity cannot be verified.