The release date for the game is scheduled to be June 29, 2017 in Japan. It is a full remake of the original, time travelling RPG released in 2010, with new scenarios. It will also have other new elements.
More information on the game will be featured in the April 6th issue of Weekly Famitsu magazine (releasing on March 23, 2017), with a six-page scoop of the new RPG that will include comments from the development staff.
The teaser website can be seen here.