Phantom Time refers to a hypothesis advanced by several scholars, most notably the German systems analyst Heribert Illig. This hypothesis states that a 300-year stretch of time comprising the "Dark Ages" or Early Middle Ages (614 AD to 911 AD) is fictional. The history of this period was invented by later writers for political or theological reasons or simply to fill the chronological gap.
When the Gregorian calendar was introduced to replace the Julian calendar in 1582, there was a discrepancy of ten days and an adjustment had to be made for this discrepancy. The problem with this is that the discrepancy should have been for thirteen days instead of ten. The ten day discrepancy implied that the Julian calendar had been instituted in 325 AD instead of 45 BC. The ten day discrepancy would make sense if a three hundred year period of time had been added to the chronology without any calendrical adjustments made when this occurred.
A possible explanation for the ten day discrepancy is that the Julian calendar was introduced in 325 AD by the Council of Nicaea. One of the goals of this council was to establish a means of calculating the date of Easter. They may have adopted the Julian calendar at this time and this may explain the ten day discrepancy. However, there is no direct evidence the council actually did this.
Scientific dating problems
Carbon-14 dating is not suitable for timescales as short as the period of time involved in this hypothesis so it cannot be used to resolve this issue. Dendrochronology does not work either because there are not enough extant pieces of wood from this time period for accurate dating to be done. Supporters of this hypothesis argue that this is because the few examples of wood from this time period have been misinterpreted and there are actually no samples from this time period because this time period never existed.