Season one start dates has just been announced as follows :Friday, August 29th :
Asia: 1:00 a.m. KST (UTC +9)
Europe: 9:00 p.m CEST (UTC +2)
Americas: 6:00 p.m. PDT (UTC -10)
Please note that these times are tentative and subject to change though it'll be updated by a blue post in the official forums if start times change.
Patch 2.1 will be released before the first Season starts allowing people to download and test the new mechanics first.
Servers are likely to be patched tomorrow over to version 2.1.
Site imports may be disabled while patches are made to the site to make things work properly with the new patch.
I'll be looking forward to playing patch 2.1 along with Seasons but will be devoting some time into making this site compatible with patch 2.1 and developing whatever additional seasonal metrics from the community API.