Metaphysical / Paranormal event
A period of approximately 31 years (as few as 19 to as many as 94) where the world was in such disarray that traditional time-keeping was unreliable. The beginning of the Lost Years is generally held to have begun during the Sundering with the Cleaving of California, includes the events of the Convergence, and concluded with the start of the Year of Convention.
The Lost Years is a period of history when the human societies of Terra were in such disarray, they were unable to keep track of time. Methods of keeping time existed, but could be unreliable (or were used unreliably). The Lost Years is considered to be a period of 19 to 44 years, which ended with the Convention of Mechanus. According to the timekeeping of Primus, 31 objective years had passed between the Sundering and the Convergence and the end of the Convention of Mechanus. However, due to planar phenomena and mortal subjectivity, different regions and peoples believed as few as 19 years or as many as 44 years had passed.