Source: NA WG Customer Service Center
We will be performing server maintenance on Tuesday April 18th, 2017 for the release of Update 9.18.
Maintenance will begin 1:00AM PDT (08:00 UTC) and will last approximately six (6) hours. During this time, the World of Tanks servers will be unavailable.
After the maintenance has completed, please run the World of Tanks Launcher (WOTLauncher.exe) to ensure that the game client updates properly.
If you selected the option for automatic updates in the World of Tanks Launcher ensure that the game has finished updating.
Should you encounter any issues while updating the client please contact our Customer Support department by submitting a help ticket.
We appreciate your patience and understanding.