This one wasn't as good as some other recent episodes have been, but it still had its moments. Most of all, its plot reminded me of the cryptic Kanto stories that had some kind of legend interwoven into them ("The Ghost of Maiden's Peak", "The Ancient Puzzle of Pokémopolis", etc.). Anything that's a throwback to the first season is okay in my book.
This is also one of those not-often seen episodes where Ash is completely separated from the group for nearly the entire episode's duration. And here it worked, because the others going along with him would have made it more of a hindrance and they wouldn't have contributed much (unlike, say, "The Tower of Terror", where I believe Misty and Brock would have helped the story).
I did like the story they wrote around Baltoy, but it seemed to drag in a few places. And the title was kind of a dead giveaway - had the word "Time" not been included in it, I doubt I would have figured out so quickly that the woman was Calista's future self. But still, it was a decent episode, and it's nice to see Xatu again, at least.