Elder Scrolls Online is officially welcoming back beta participants on April 16th at 10:00 am. EDT. The free trial lasts through Monday, April 20th at 10:00 a.m. EDT. Zenimax is also running a weekend giveaway featuring various in-game prizes that you can enter by simply logging in for two or more hours.
There’s also a roleplaying ball with storytelling, riddles, dancing, and party gifts, as well as a scavenger hunt and trivia event, all of which are hosted by player organizations. A full list of the festivities is posted on the official ESO website.
[Source: Announcement post and full schedule]