Time travel

Time travel (or time-travel) is the concept of moving between different points in time in a manner analogous to moving between different points in space, generally using magic. Beings can travel forward, backwards, or sideways (hence visiting an alternate universe, as in Warlords of Draenor) through time and have the ability to change history sometimes (like killing Hakkar) or steer a timeline towards an alternate future (as what happens when Murozond sends adventurers to the End Time).

Medivh explained two different theories of time to Khadgar while he was still an apprentice. One followed the most common idea of a sequential series of events, while the other was one of predetermined history. He used the comparison between a clock and a sand time as a metaphor to explain himself. With a sand timer, all the events in time are there, what order in which they are determined (passing through the sand timer) is random, but that which we experience and see will appear to be in order, and still have the same outcome. Both theories share the idea that nothing people do can change the future, they need only play their part to lead up to it.

Teleporting to the future is called chronoporting.

Caverns of Time
Located in the eastern part of Tanaris, the Caverns of Time contain various portals to different key historical periods and events in Azeroth history. The caverns act as a crossroads for the various timeways, and through them one can travel back and forth along the ebb and flow of time. The Bronze Dragonflight protect the Caverns of Time and seek to make sure history is unchanged so that the timeways are not altered. Usually, the Keepers of Time are tasked with normal maintenance and fixing ordinary minor disturbances like rogue mages changing something in the past to elevate their status or wealth in the present. More serious attempts to dramatically alter history are usually perpetrated by the Infinite Dragonflight and require more attention.

War of the Ancients
The events of the War of the Ancients were visited at least twice; first by Rhonin, Korialstrasz, and Broxigar. Then the adventurers of the Horde traveled to the past to the site of the Well of Eterntiy in order to retrieve the Dragon Soul. Adventurers of the Alliance then traveled to a potential future in the Dragonblight region.

Twilight of the Aspects
During the war against Deathwing, Thrall traveled to alternate timeways of the past, including a world where Aedelas Blackmoore conquered Lordaeron.

Warlords of Draenor
The events of Warlords of Draenor take place in an of an alternate universe situated 35 years in the past in comparison to our universe. To illustrate this: at the same point in time (when the Dark Portal opened), it was Year 31 in the main universe but at the same time Year -2 in the alternate universe.

Legion
Elisande used her powers to rewind time during her last encounter with the adventurers.

Chromie and an adventurer traveled into the future in order to prevent her death at the hands of an unknown assailant. She also rescued her previous selves in Andorhal, Stratholme, Mount Hyjal, and the Well of Eternity.

In Hearthstone
Toki, Time-Tinker is a time traveler. Infinite Toki is implied to be the future version of her.