Let me start off by saying that it has been a while since I really liked the concept and storytelling of a drama this much.

Having watched mostly korean and some chinese dramas I had no prior experience to taiwanese dramas.
So after seeing the unusual high score of this show on MDL I was a little hesitant to start it. Was it another overrated drama that the fandom pushed into the high ranks by force? After having watched it I can say for sure that this is not the case. It does deserve all the praise it is getting!

--Story--
The first episode starts out really slow and gave me a bad expection of the show to be honest.
All these quirky side characters and the scenes at the company reminded me of old korean shows from 10 years ago.
What kept me watching was the relationship between the female lead and her lost boyfriend and I am glad that I did.
The disappearance of the male lead was shrouded in mystery and at first not a lot of information was handed out.
After a while you get to realise that he is probably dead.... or is he really?

The storytelling of this show is a big plus and you realise that everyone involved took a lot of planning and focus to detail in creating this show. Only sparely information is presented and the focus is mainly on the love story between the male and the female lead. The interaction between the cast members, especially in the past, fills in the lack of actual information perfectly. You try to put together the puzzle pieces in your mind and it keeps you focused on the story. You laugh at the silly banter and feel with the main leads sadness. The thriller aspect could have been done a little better (the villian and his motives were a stark contrast to the rest of the story) but in general the show does a really good job at it. After lovely fluff between the main lead you get upset at all these tragic things that keep happening.


--Acting--

A big big plus of the show. As said before this is my first taiwanese drama so I knew none of the actors. I was especially impressed with Alice Ke since she had to portray two vastly different characters and did a really good job at it. In the beginning I felt Huang Yu Yuans sadness of losing the love of you life and the constant battle of trying to forget him and towards the end I could really understand the problems of Chen Yun Ru who felt alone in this cold harsh world.
The bromance between Greg Hsu and Patrick Shih was super fun to watch as well and I will guarantee you that you will cry once because of it if you start watching this show.
The acting made the show a ton more believable and enjoyable.

--Music--

What is to say here. On of the best Soundtracks I have heard in a while. Starting with the Opening Track which I never skipped to the time travelling Wu Bai "Last Dance". I can't get that song out of my mind for a long time. I loved every musical piece in this drama. The music was a big reason some scenes felt so emotional. You traveled back in time with the female lead while listening to it.

--Final Thoughts / Rewatch Value--

To summarize" Someday or One Day" I would say it is a nice blend of a beautiful love story with an excellent cast + the time travel shenanigans of the german tv show "Dark".
Compared to the big production korean dramas I watch usually this show was a breath of fresh air.
Even though not a lot of money was involved in producing this show you can feel that the production crew really cared about it and focused on the important aspect. Honestly do you need fancy production when the story, acting and music is this good? This show will stay in my mind for a long time and I will surely rewatch it in the future.
When you browse the internet for discussion you realise how many small details you miss that show you what kind of long planning and care took place to create this gem.