The laws of physics vary from universe to universe, and within those precarious frameworks reside various methods of circumventing the natural order of time and space. Among those who achieved mastery on temporal manipulating are the superhumans that donned in the early part of the 20th century.
While a young Superboy on one world achieved time travel by travelling faster than light, the preferred method over time was by using his teammates' Time Bubble to journey from the 20th to 30th centuries. Elsewhere, and elsewhen, the original Superman utilized the faster than light technique to witness the destruction of Krypton-2.
Perhaps the best at traversing the stream of time are the Flash of Two Worlds. Barry Allen recognized early in his career that the energy expenditure necessary to reach another decade or century was prohibitive, especially given the lack of precise control at when he'd arrive at his destination. So he invented the cosmic threadmill. His counterpart Jay Garrick seemed to manifest greater ability at finding a specific era and moment with said era using only his powers, although he devised his own variation on Barry's technology.
Their teammates the Atom each enlisted the aid of scientists in their attempts at reaching historical periods in the past, with Ray Palmer diving repeatedly into Professor Hyatt's Time Pool and Al Pratt alongside his Justice Society pals using a Time Chute among other devices.
Then there was the awe inspiring powers of dopplegangers Time Trapper and Tibro who bent time to their will while bedeviling the Wonder Women. Although on another occasion, it was Earth-Two's Doctor Doome who substituted for Tibro attacking his world's Law's Legionnaires through the centuries as had the Time Trapper in his battles with Legion of Super-Heroes on multiple occasions. And while Doome had encountered the Justice Society as a member of the Time Trust on a prior occasion, so had his doppleganger Doctor Anomaly early in the Justice League's career. On each occasion, the forces of good prevailed over that of evil, time and time again!