A sign which shows the exact date and time of artefact and building plan release has been implemented to the game. It appears 5 days prior to those events, and shows the release time with a second precision. The artefacts and plans are instantly conquerable when they are released.
This only applies to the T4 servers, meaning servers beginning with 'ts'. Example: ts2.travian.com
At least for now, I will continue to announce the dates here in forum also. People not playing in the server would not be able to see the counter sign even though they might still be interested in the progression of the game round.