or dramas associated with multi-universe haha 

Ashi Girl - historical, comedy, romance, scifi
Boku Dake ga Inai Machi - thriller, supernatural
Joy of Life - mystery, fantasy, wuxia
Juunen Saki mo Kimi ni Koishite - romance, scifi
Please Don’t Spoil Me - crossworlds traveller, comedy, romance
Returner - movie, combination of terminator, matrix and many others

^^ty 410euros and kardasx for the recommendations

Circle - Past & Future every episode. Unexpected ending out of the three; in a good way.

The King: Eternal Monarch (2020) - two worlds & time travel.

Reunited Worlds (2017) - simplest one out of three.

Truly the best time travel drama is Signal it is just out of the world amazing and definitely a must watch.

Other good ones are;
Someday or One Day (Taiwanese drama)
Reset (chinese drama)
Train (kdrama)
Kairos (kdrama)
365: Repeat the Year (kdrama)
Moon Lovers: Scarlet Heart Ryeo (kdrama)
Tunnel (kdrama)

Jin (Japanese) - two seasons, but the story is continuous. I haven't seen the Korean remake, can recommend the original. A brain surgeon finds himself back in time in the Edo period.

The King: Eternal Monarch , it's the only one I have watched so far

Ashi Girl is my favorite, so fluffy, adorable. A school girl that insists of going back and back in time to visit her crush in ancient times.

Is "being transfered into game with historical setting" also considered as time travel? If yes, then: My Queen - FL is transfered from a modern time to a game world, where she becomes princess and sets out on a funny adventure to find her true love. :)

Korean crime thriller Tunnel - loved the main lead and though it's set up like a crime thriller, it is also a time travel of sorts.
Chinese fantasy Lost Love in times - loved the political intrigue and the various princes surrounding the FL.

Somebody asked the same question in this thread.

If you're happy to watch BL, then "Once Again" is good.

Some of the ones I've watched:

Tomorrow With You - travel into the future

Tunnel  - travel into the past

Blue Birthday - travel into the past

Shining For One Thing - travel into the past

Someday or One Day - travel to the past but it's not as simple as that. It's a spoiler so I won't get into the details. The show is worth watching.

 

Mr. Queen and Moon Lovers Scarlet Heart Ryeo