I won't make this review long because I would basically be repeating what everyone and their mother commented.
if you have 16 hours to kill then go ahead and watch this drama, otherwise don't bother. especially if you care a lot about the plot, because it feels like a 15-year-old drafted this story after watching some youtube videos on time travel (and still not understanding anything). the ending was one of the worst kdrama endings I've ever witnessed among all 40 or so dramas that I've watched so far. so many plotholes and loose ends. weird incest romance thing. so goddamn unfair to the characters who went through so much and it all felt useless at the end, especially min hyuk and do yeon. they didn't deserve such a dissatisfying end, ugh. the only thing that kept me going was the actors. it truly felt like a waste of an amazing cast and a promising premise. sigh... but ill admit guiltily that i still found it entertaining to watch. make what you will of my review.