Time Bridges are Horomancy devices used to travel back in time to a specific date.
Time bridges were constructed with a piece of a rare element that was eventually used depleted by the 1970s. Prior to then, bridges were erected to Ancient Rome, the Cretaceous period, and to Southampton, England for the voyage of the Titanic.
A thesis paper was submitted by Benjamin Issac, a previous Brakebills student, on their plan to kill Adolf Hitler. The project, dubbed Operation Die Hitler, included a time bridge to April 19, 1942. The thesis was scrapped after the students involved died at the hands of Hitler, and the bridge was sent to Brakebills' archives.
Hitchiking to Fillory
In 2016, Julia Wicker and Quentin Coldwater searched for a way to travel back to 1940s England in hopes of catching a portal to Fillory in order to catch up to the Brakebills group on a mission to fight The Beast. The pair went to Brakebills, which Julia used Richard Corrigan's Alumni Key to enter, and began looking through past time bridges.
During their search, Julia found a previous time bridge created by Benjamin Issac for a failed assassination of Adolf Hitler dated for April 19, 1942. Upon hearing the date, Quentin recounted a moment in The World in the Walls when Jane Chatwin went shopping for a gift for her brother, Martin. Realizing the time bridge would bring them within days of the book's events, Julia and Quentin brought it with them to London.