Diablo III is scheduled to go offline for maintenance today for the deployment of patch 1.0.5, however not all region’s servers will go down at the same time.
The servers are due to go down at 3:00AM PDT and should be back up by 1:00PM PDT. You can check out when maintenance will begin in your region here. If you’re interested in what patch 1.0.5 includes then you can check out the full patch notes here.
“Please note that you will not be prompted to download patch 1.0.5 until the patch is live in your home region. If you are logging in from a European or Asian client, you will need to wait for this patch to release in that region before it can be installed. Additionally, if your home region is the Americas, you will be unable to log into Europe or Asia using Global Play after patch 1.0.5 is live until those regions have also patched,” Blizzard said on the Diablo III official forums.