Any hint how to get it?
Find an Orange Tree. Go South from the Orange Tree until you encounter a Red Tree. Go West from the Red Tree in a straight line until you reach your destination. Make sure you are starting from as close as possible to the trunks of the trees and walk in a straight line. If done correctly then you will get there once you walk far enough. For context, sprinting with 3X frame rate still takes a couple seconds of movement past the end of the "path" that will become visible after solving a different puzzle.
No, the time of day in the forest doesn't matter. You just need to follow an invisible path down from an Orange Tree until you reach a Red Tree. You then go left from the Red Tree and you will encounter the zone with the Harbinger. As long as you line yourself up with the center of both trees you will reach the destination you seek. There are no prerequisites aside from following the path.