Steins;Gate, Zetsuen no Tempest Recommendations
Both anime have time travel theme, but one is time traveling to correct/bring back to original what shouldn't have been done while another time traveling which leads to the current state. Which is which is for you to find out.
The both tackle with time travels and their logic.
Both have a cast of strong leads(although Steins;gate gets the edge in character interaction), are thought-provoking with a very intricate and well-thought out plot, in the middle of which the lives of certain characters are ended, serving as a driving force for others, an overreaching power as a villain which the cast does not know about immediately and oh, both involve time as an important part of the plot. Also, The two have certain plot holes too you will have to overlook but if you can ignore the ones in Steins;gate, you won't mind the ones in ZnT, and vice versa.
This one of my favourites animes.
The history it's very, very, very, good, amazing, it has got a lot of intrigue (well, I think that, it's my opinion) and a little of comedy, but mainly, is serious and well, I really recommend it a lot. It has got an OVA and a movie. The visual novel is very good too.
Not many seem to relate these two, but I think besides Mahou Shoujo Madoka Magica, "Zetsuen no Tempest" is very similar to Steins;Gate because both portray a Well-Devised Plot and Sense of Complication. No further spoilers. Watch to find out! It's worth it! :P
Both seem nice and sweet, but then change into a dark, serious, and mysterious show.
Steins;Gate has things covered in terms of accidental discoveries that has gigantic potentials in disrupting the flow of the world's natural time. Just like Zetsuen no Tempest, Steins Gate focuses on the unexplainable mystery of the world while trying to go against it and return the world back to the way it is.