Here is the EUW Riot NOC announcement:
"Summoners,
Starting at 20/08/2013 11:30pm UTC, ranked queues will be disabled in preparation for a server maintenance at 21/08/2013 1:00am UTC, the servers will be shut down and all games currently in progress will end in a draw and stats will not be recorded. We estimate the battlegrounds will be unavailable for 6 hours."
and here is the EUNE Riot NOC announcement:
"Summoners,Reminder: These announcements mention no patch or new content.
On 20/8/2013, starting at 09:30pm UTC, ranked queues will be disabled in preparation for a server maintenance. At 11:00pm UTC, the servers will be shut down and all games currently in progress will end in a draw and stats will not be recorded. We estimate the battlegrounds will be unavailable for 6 hours."
