Inf you want a short review, I thought this drama was absolutely mind-blowing and so much creative thought was put into it. If you want a long review...then please continue reading:

WARNINGS: (*DO NOT READ THIS IF YOU DO NOT WANT MAJOR SPOILERS*)
WARNINGS: For the sake of keeping this as short as possible, I actually DID NOT talk about Ye Jia Cheng in this review)

So the first thing I want to say is this drama WAS ABSOLUTELY MIND-BLOWING. Here's why:

The beginning captured me, yes, but the end was absolutely fascinating. The whole drama was centered around the idea that the main female lead had traveled to the past through the incidence of an airplane's turbulence. The man sitting next to her on the airplane had protected her in that situation, and regardless if it was fate or not, it definitely led to their lives becoming intertwined. Through so many more situations in the plot, the main female lead is so heartbroken she decides to once again get onto the plane again because she wants to travel back to the past AGAIN. Even if she dies, it would be better than living a life in misery. The man decides to get onto the airplane with her, not knowing that he had also previously been on this plane in the past. After the airplane sets off, the female lead does admit that this has all happened before, and perhaps it's fate. However, this time, the female lead is the one who protects the man on the plane. (I'm excellent at being bad at explaining plots, I apologize for this but please continue reading.) ONCE THIS ALL ENDS, the female lead wakes up in a hospital. She realizes that this is the "future" (it's more like the present) when she had first gone through the first plane turbulence. Apparently, the entire drama had been a dream she had while she was in a coma. HOWEVER, when she exits the hospital, she sees the man, and the man has flashbacks of the entire drama. SO, was everything actually just a dream? NO, I DON'T THINK THAT'S IT. I believe she really traveled to the past, went on the SECOND plane ride, and went to another "future", "past", "present", or even another dimension (??) where life continues on as her first life, and the wish to travel back by getting on the second plane ride was fulfilled.

Other ideas I realized (that were mind-blowing FOR ME):
-the man and the female lead previously talked about the idea of whether wishing for something would really make it come true (this helped me realize that she indeed did wish to travel back to the "future" and it came true)
-This honestly might not have any meaning, but the native name of this drama is "Shi Jian Dou Zi Dao". Based on what I've learned in Chinese, it means "Time also Knows." However, the main female lead's name is Shi Jian (but using a different pinyin from what "time" uses). So does the title actually mean "Time also Knows" or "The Main Female Lead also Knows"? Of course, my Mando isn't that good so I'm not sure if this means anything or if I'm right. I just thought that this was super mind-blowing.
-Yi Pei: I feel like he wasn't selfish and selfish at the same time. It's as if he loved the main female lead so much, but he didn't understand how to approach love because he's never felt that kind of romantic feeling towards someone before, that his love was so pure. (Regardless of how I've seen his dark side towards approaching love I believe it was all out of pure, utterly innocent love.)
-At the end of the drama, I feel like the two of them silently agreed in their hearts that both of them had remembered the "dream" and had experienced it. And yet there are so many layers or details to it that I also feel not only did they both silently agree to that in their hearts, both of them also aren't even sure if the other person remembers.