Kang the Conqueror (Marvel) is the most important time traveler in the Marvel universe.
Superboy (DC) can travel in time but cannot change the past as the following comic book page demonstrates (Superboy V1 #85).
The Time Trapper (DC) is probably the most powerful time traveler in the DC universe.
Kang’s Time Chair (Marvel) is just one of many technologies Kang uses for time travel.
The Legion of Superheroes-Time Bubble (DC) is used by the Legion of Superheroes from the 30th century to recruit Superboy from the 20th century.
Rip Hunter Time Master has a Time Sphere and the series revolves around time travel.
The Time Machine (Dell) is a comic book version of the movie which in turn is a comic book version of the movie. The movie and comic book are inspired by the H.G. Well’s book of the same name.
Various time machines are shown in the Star Trek and the Legion of Super Heroes.
The Atom (DC) often used the Time Pool to have adventures in the past during the Silver Age. The Atom adventures did teach a little history unlike most such adventures in comic books (The Atom V1 #3).
Captain Sprocket fights Mr. Clock who can jump five minutes into the future in Archie’s Madhouse #45.
Gary Seven travels from the future to the 20th century in Who’s Who in Star Trek #2 (DC).
The Great Race of Yith have conquered time in Field Guide to Cthulhu Monsters.
In “Industria” Heavy Metal #282, a time traveler creates a time traveling toilet.
Tales to Astonish (Marvel) featured several time travel stories with a twist!
Tales to Astonish V1 #3
Tales to Astonish V1 #11
Tales to Astonish V1 #20
Tales to Astonish V1 #29
Tales to Astonish V1 #33
The Tempus Twins can jump five seconds into the past in Creature Collection II. Dark Menagerie.
Time Tunnel #1 (Gold Key)
Chronos – Clocks – DC Heroes-DC Technical Manual
Judge Dredd – “The Time Machine” – 2000 AD #889
Mother Earth – 2000 AD #871
“Only Time Will Tell”- Weird Fantasy #13 (EC)
Poseidon (DC) travels to the future to woo Mera (DC) with magic pod in Aquaman V1 #17.
Rip Hunter-Time Backpack – DC Heroes-DC Technical Manual
Tardis 2 – Second Doctor Sourcebook
Tardis 3 – Third Doctor Sourcebook
Tardis 4 – Fourth Doctor Sourcebook
Tardis 5 – Fifth Doctor Sourcebook
Tharg’s Future Shocks – “Bone Shaker!” – 2000 AD #715
Time Flies – 2000 AD #1015
Vector 13 – “Operation Mordred” – 2000 AD #968
The Marvel universe gives Old Man Logan their opinion of trying to travel to the past in order to change events in Old Man Logan #19.