Overview

The year 400 (CD) was a leap year in the Julian calendar that, by convention, began on a Sunday. In contemporary Roman usage it was identified as the Year of the Consulship of Stilicho and Aurelianus and sometimes counted as 1153 Ab urbe condita (from the founding of Rome). The numeric label "400" became widespread in Europe only after the early medieval adoption of the Anno Domini era.

Political and military context

The year sits in the period historians call Late Antiquity, when the Roman world was divided politically between East and West following the death of Theodosius I. The Western Empire was governed under the young emperor Honorius with powerful generals and court officials exercising real authority. One such figure, Stilicho, held the consulship in 400 and dominated military affairs in the West. External pressures from migrating tribes and emerging barbarian kingdoms increasingly shaped imperial strategy and territorial control.

By 400 Christianity had become the dominant religion within the Roman state and shaped law, charity, and public life. Urban centers continued to be important administrative and economic hubs, though trade patterns, taxation burdens, and ruralization were changing the social landscape. These shifts contributed to regional diversity across the Mediterranean and to new local powers filling gaps left by weakening central control.

Chronology, calendars and naming

The Julian calendar, instituted by Julius Caesar, treated every fourth year as a leap year; hence 400 was such a year. For people in late Roman territories events were dated by consular names or by regnal years; later medieval scholars standardized many references using the Anno Domini system. The medieval and modern study of this period therefore relies on cross-referencing multiple era systems and surviving documentary evidence. For a reconstruction of the year's placement in the Julian cycle see the full calendar.

Significance and notable figures

While 400 itself contains fewer universally famous single-year events than some other dates, it exemplifies a moment of transition: imperial institutions persisted even as military leaders, migrating peoples, and religious institutions reshaped the map of Europe and the Mediterranean. Notable figures associated with this time include Stilicho in the West and various regional leaders whose actions over the next decades would culminate in major changes to Roman western provinces.

  • Consuls: Stilicho and Aurelianus
  • Calendar labels: Year 400 AD; 1153 Ab urbe condita
  • Historical phase: Late Antiquity / Migration Period

This year should therefore be read as representative of a broader era of transformation rather than as an isolated turning point: administrative continuities, growing regional autonomy, religious consolidation, and external migrations together set the stage for the historical developments of the 5th century.