Omg this is a hard one, but I think Splish Splash Love takes the win. It was short, sweet, undeniable chemistry, and well put together.

Mr. Queen is a close second.
Also special shout out to Tomorrow with you. That drama had some really brilliant moments, plus SMN and LJH had great chemistry.

It’s not even a contest. Signal is one of the best kdramas of all time.

Splash Splash Love because it's the only Time related drama I like period 😂😂😂
#AllergictoTTProblems

(Shout out to the first 10 episodes of Queen In Hyun's man that I watched in a subliminal fever dream on my phone in 420p, in Canberra, Australia, in 2016, when I was so sick I could barely leave my hostel room for three days, that I will never be able to finish because the state I started it in is too ingrained into my subconscious and impossible to replicate though...)

Splish Splash Love! And I just watched Kairos so that's up there for me too.

I love nearly every drama listed here but I'll have to agree with @mistyisles. Life on Mars is absolute perfection. The setting works so well for the show and the way they intertwined real-life issues and events with the drama was amazing (like the hostage situation or the way 'vagrants' were removed).

I don't know if Kairos would technically be considered a 'time-slip' drama but it's also very good especially when you reach the end of Ep. 6.

My two favorites are Mr. Queen and Splish Splash Love, but it’s Mr. Queen by a photo finish. These two are also on my list of Happy Place dramas. And I love both Shin Hye-Sun and Kim Seul-gi; they are terrific actors.

Mr Queen!

Signal

Despite the admittedly disappointing ending it has to be MR. QUEEN for me. Not just because Shin Hye-sun is my very favorite actress but may be because it shows why she is my favorite: Her extraordinary performance.

SPLISH SPLASH LOVE is a good runner up.

It’s impossible for me to pick any kdrama. Because Someday or One Day happened.

Well, I was going to have a lot of trouble with this, but then @mistyisles came up with the best justification for excluding Signal on a technicality, so I get to pick Live Up to Your Name with fewer reservations.

I love it for all the obvious reasons: Kim Nam-gil, every facial expression known to humankind, satisfying storylines for both main characters. But it also holds a special honor as being one of the dramas that has made me ugly cry the hardest. And you just can't forget a drama like that.

I know I'm only supposed to pick one, but, these two are equally awesome for such different reasons I honestly can't choose.

Queen In Hyun's Man for being the first drama I binge watched literally start to finish, featuring what is still after all these years one of my favorite male leads and my top romances. Loved how said male lead cleverly used time travel mechanics to achieve his goals in the past, and the drama-within-a-drama tie in between the two eras.

Then Mr. Queen, for all the reasons already mentioned. The funniest K-drama I've ever seen, zero contest. And as I happen to be in that minority of viewers who liked the ending, it's one of my favorite dramas, period.

Can't choose between Live Up to Your Name, Nine, and 365 Days, sorry.
But I do know that Faith is in the 4th place after those 3, if that is of any help 😂

Mr Queen comes first, undisputed.

Kairos comes close first.

Second - I could be one of the few or many who liked Scarlet Heart Ryeo from start to finish. My one cross - the 13th prince didn't have to die. And his wife who's only wish was to be independent of her father's air became collateral damage in the royal shenanigans/King's curse whatever.

I thought Splash Splash Love was a modern kdrama due to its title. Never did it occur to me that it's a Saguek.

For a kdrama I guess SIGNAL was the most enjoyable for me.

I generally don’t like time travel dramas since the time paradox explanations always confuse me. And especially with romantic dramas there always seems to be an inherent sad or unsatisfying ending, think Moon Lovers

The anime YOUR NAME is the only time travel film that I’ve truely loved with all my heart. Everything else pales in comparison and nothing comes close to such perfection imo. It’s one my absolute favourite films of all time

This was ridiculously hard as I now realise this is one of my favourite genres. The different means of transport fascinates me and if more than one person has the ability to travel or the character go back and forth between the past and present. It has to be Go back couple for me because I love the way the story plays out; it’s a proper rom com and it tackles another element that is often missing from this genre the losses and gains of the people in each time period. Her joy of being back with someone she misses in the current time period was so real and must have touched a nerve for others who wish they could have that opportunity in real life. I love the way they show the difference the experience made in their lives.

So many honourable mentions:
Mr Queen using a gender and class swap as well as time travel was just so hysterically funny.
Live up to your name; helps rebuild a father and daughter relationship, brings history alive and shows people using truck of doom to their advantage.
Miss granny (film); I love how it changes an Ajumma’s perspective on her current day behaviour.
The light in your eyes; so many hate this drama but I love it for the way it depicts an experience exactly how people describe the experience feels in reality.

Queen In-hyun’s Man for me. Kim Boong-do is one of my favorite characters. He was so smart and resourceful.

I’d pick Faith, only because it was the one that introduced me to this trope, and I was still in love with LMH when I watched it. I was new to Kdramas then and I wasn’t cynical yet. I recall thoroughly enjoying it.

I also enjoyed Mr. Queen and Signal, but I was no longer blind to their flaws when I watched them.

Live Up to Your Name, period.
It’s a sad story though, considering what enables them to travel through time. But I have to pick this one for the story, KNG, his comedic timing and chemistry with FL. They are the cutest couple in Kdramaland in terms of body gesture of people in love. They look really comfortable being with each other, too, and that is just so special.

I’m going to ho with Faith - the wormhole, the secret gate, the general in Goreyo armor wandering around a 21st century city, the lovers passing by like ships in parallel universe nights, the message in film cylinders … And although a lot of the time slip part’s didn’t make sense, the love story was charming (as Lee Min Ho is known for).

Like @missvictrix, Nine is my all time best time travel drama. It was so compelling and Lee Jin Wook’s acting was daebak! I felt his emotions. This is in my top 10 dramas.

I just have to say that my runner up is Queen In Hyun's Man. Very under-rated but wonderful drama. I think I want to re-watch this.

Oh but if we're doing movies, and not Korean related content at all, and if it counts, then honestly, 100% 君の名は。
/ Kimi No Na Wa/ Your Name, every time, for all of time.
One of the only other exceptions to my allergy.

Time Travel dramas are quite good to watch when the writing is on point. Some dramas have failed and kept us so confused with it because the writing falls so short.

The best of all Time dramas
1.SIGNAL- Kept us on edge from beginning til the end.
2. Queen in hyun's man- This fusion Saeguk is love.
3. Splash Splash love- So cute this one.
4.Life is on Mars- Brought the 80's vibe
5.Tunnel - A good ride for this one

Live up to your name, hands down. The only drama I have completely rewatched, from start to end.
I couldn't move on when I finished it the first time and even now it's often on my mind. And it made me know Kim Nam Gil, so forever thankful.
And please, we need that second season which Unit asks for, Drama gods.

Honourable mention: The best hit.

As I am quite new in Dramaland I have lots of series in my Plan to watch list and I love time travel sub-genre, so I'm going to watch almost everything beanies recommend.

Live Up To Your Name.

I have a handful on my list: Signal, Splish Splash Love, Queen Inhyun's Man, Tunnel, Live Up to Your Name and Mr Queen.

Omg i was just about to start Nine: Nine Time Travels because i love mystery and time travel dramas and poof! There is this list! I'm going to try watching it. Thank you!

There are so many dramas with this theme...

I think Splish Splash Love was the most simple of all : no murderer, no stealing body, no reincarnation, no brain tumor, no changing the present, etc. It was simple, cute and short!

But there were good ones too with Signal, Life on Mars, Queen and I, Live Up to Your Name.

There are good Japanese drama/movie too. One of my favourite is Todome no Kiss.

Signal is number one.
Rooftop Prince my number two.
Life on Mars is perfection

I can't pick. :(

I really liked Queen In-Hyun's Man and Mr. Queen, but they both suffered from the same issue that the drama wrote itself into a corner and couldn't perfectly execute the final time slip.

Nine is one of my all-time favorite dramas, and Blue Birthday tried to replicate the magic using a different storyline, which shows its relevance to kdrama culture.

But I'll have to go with Splash Splash Love as the final winner. Short yet sweet with an adorable couple. I love how the time travel situation helps both our leads with their self confidence.

This is way too hard and it made me realize how much I love time-slip stories! I vote a resounding yes to every one mentioned.

I've got to vote for 'Tomorrow with You' (2017) largely because... well... Shin Mina. I also preferred Lee Ji-hoon's character in this series to his character in Signal. Signal was too much murder and mayhem for my taste. Give be a twisty-turny times slip romance instead.

1. Queen In-hyun's Man
2. Nine: Nine Time Travel
3. Signal

I will choose Radiant just to represent .

So may time travel shows are on my K drama favorite list.

Non K drama
A funny Chinese time travel & gender swap to boot Go Princess Go
Another C drama they did well was Bu Bu Jing Xin

I'm going to say Signal because it is objectively brilliant TV in every way.

However, there's only 1 Kdrama I have ever watched 3 times, and that is Queen In Hyun's Man, which also falls into this category and if you haven't seen it, go treat yourself, NOW!!!!!

No love for Dr. Jin? Well, I never got through all of it, but I have this (possibly faulty) memory that it was the first time I saw a kdrama and I thought wow, this stuff is amazing, the actresses are so good-looking (first time I saw Park Min-Young), and this time-travel plot is so innovative. And then Faith and Rooftop Prince came out the same year.

1. Queen InHyun's Man - Kim Boong Do is the GOAT of all time-travellers, used Korea's advanced transpo even used his knowledge of Hanja. and I'm a sucker for Queen InHyun, must have watched at least five dramas with this Queen.

2. Nine - Nine times Time travels - this is a time-slip drama done right. Should be the manual for time dramas.

3. Mr. Queen/Live up to your name

4. Faith - the only LMH drama I watched religiously while on broadcast. Probably the only LMH drama I watched from start to finish.

CHINESE
Bu Bu Jing Xin - Scarlet Heart Ryeo won't surpass this in my heart.

JAPANESE
Dr.Jin - nice to be a doctor who can save loads of lives.

Queen In-hyun's Man would be my pick.
There are others that i have enjoyed very much... but Queen In-hyun's Man got me on my feet since the beginning and i would watch it over and over again.

Of all of these you've mentioned, Mr. Queen is my favorite. It made me realize that the point of time travel drama is frequently a critique of elements of the contemporary society of the writers. Though I did like Signal, I think the use of time travel in a murder mystery/police procedural context isn't the same. It turns the story into one about how people grapple with violence and loss in their past. Obviously I've liked those too, but it's not the same kind of thrill. I am excited to watch the two dramas in this list that I haven't seen yet, and to check out what other commenters recommend.

Hahahahaha i love how a lot of people are like “i would pick Signal but technically….” and then chooses another drama. Why make us pick just one DB?! 😄

Queen In-hyun's Man/Queen & I is my #1 pick.

A close second: Go Back Couple/Confession Couple.

I guess I really need to see Signal!

Time slips are not my favorite genre; they MUST be well-done and follow the rules created for that particular drama's "universe."

Nine: Nine Time Travels
Splish Splash Love
Mr. Queen!

In that order

Hmm... It's Mr Queen. It has to be 😆

I just finished it some days ago but I keep going back. Before Mr. Queen, I would have said Splash Splash Love though. It's my favorite drama by KSG.

Honourable Mentions:

Tomorrow With You (I completely understand the characters for some weird reason 😃)
Rooftop Prince (the final episode really shredded me)
Signal (never finished because I was in school then and mystery crime is not my favorite genre)