here is the start and end times of the open beta.
ps4 version beta can be played without PS Plus, but Xbox will need Gold to play beta.
When do the Open Beta servers go live?
The open beta servers go live at 14:00 UTC on Friday, March 9 (or 6 a.m. PST), and shut down at 6:59 UTC on Monday, March 12 (or 11:59 p.m. PDT on March 11).
Will TERA require Playstation®Plus or Xbox Live subscriptions to play?
A Gold subscription is required to access the TERA Open Beta on Xbox One.
A PlayStation Plus subscription is not required to access the TERA Open Beta on PlayStation 4.
from Tera website
http://tera.enmasse.com/news/posts/tera-for-playstation-4-an...