By time shift (not sure if that is the correct description) I meant that you temporarily visited another time in your life; possibly the future? A portal if I am correct, means a doorway from the spirit world into our world.
A possible example of a time shift, was an incident that happened back when my husband and I were dating. I wanted a quick shower, so when he called me to let me know he was on the way, I told him that I would leave the front door unlocked so that he could let himself in. The house where I was living at the time was in a small intentional community, and I knew all my neighbors, so I felt safe to do so. As I was drying off, I heard footsteps on the front porch stairs, a knock, then the front door opened and I heard someone come in. I called out his name, but there was no answer. I called out again, and there was no answer. I got dressed and opened the bathroom door, and there was nobody there. While I stood there, puzzled, I heard the same sequence of sounds; the steps on the stairs, the knock, then the door opening. This time it was my husband. When I told him about it, he speculated that someone had gotten confused and entered the wrong house. That was not likely because the same people came and went there. But I always wonder if this was some sort of time shift!