Ides of March
The Ides of March (Latin: Idus Martii or Idus Martiae) is a day on the Roman calendar that corresponds to 15 March. It was marked by several religious observances, and became notorious as the date of the assassination of Julius Caesar in 44 BC. The death of Caesar made the Ides of March a turning point in Roman history, as one of the events that marked the transition from the historical period known as the Roman Republic to the Roman Empire.
Although March (Martius) was the third month of the Julian calendar, in the oldest Roman calendar it was the first month of the year. The holidays observed by the Romans from the first through the Ides often reflect their origin as new year celebrations.
The Romans did not number days of a month sequentially from the first through the last day. Instead, they counted back from three fixed points of the month: the Nones (5th or 7th, depending on the length of the month), the Ides (13th or 15th), and the Kalends (1st) of the following month. The Ides occurred near the midpoint, on the 13th for most months, but on the 15th for March, May, July, and October. The Ides were supposed to be determined by the full moon, reflecting the lunar origin of the Roman calendar. On the earliest calendar, the Ides of March would have been the first full moon of the new year.
Religious observances 
The Ides of each month was sacred to Jupiter, the supreme deity of the Romans. The Flamen Dialis, Jupiter's high priest, led the "Ides sheep" (ovis Idulius) in procession along the Via Sacra to the arx, where it was sacrificed.
In addition to the monthly sacrifice, the Ides of March was also the occasion of the Feast of Anna Perenna, a goddess of the year (Latin annus) whose festival originally concluded the ceremonies of the new year. The day was enthusiastically celebrated among the common people with picnics, drinking, and revelry. One source from late antiquity also places the Mamuralia on the Ides of March. This observance, which has aspects of scapegoat or ancient Greek pharmakos ritual, involved beating an old man dressed in animal skins and perhaps driving him from the city. The ritual may have been a new year festival representing the expulsion of the old year.
In the later Imperial period, the Ides began a "holy week" of festivals for Cybele and Attis. The Ides was the day of Canna intrat ("The Reed enters"), when Attis was born and exposed as an infant among the reeds of a Phrygian river. He was discovered—depending on the version of the myth—by either shepherds or the goddess Cybele, who was also known as the Magna Mater, "Great Mother". A week later, on 22 March, the day of Arbor intrat ("The Tree enters") commemorated the death of Attis under a pine tree. A college of priests called "tree bearers" (dendrophoroi) cut down a tree, suspended from it an image of Attis, and carried it to the temple of the Magna Mater with lamentations. The day was formalized as part of the official Roman calendar under Claudius. A three-day period of mourning followed, culminating with the rebirth of Attis on 25 March, the date of the vernal equinox on the Julian calendar.
Assassination of Caesar 
In modern times, the Ides of March is best known as the date on which Julius Caesar was assassinated in 44 BC. Caesar was stabbed to death at a meeting of the senate. As many as 60 conspirators, led by Brutus and Cassius, were involved. According to Plutarch, a seer had warned that harm would come to Caesar no later than the Ides of March. On his way to the Theatre of Pompey, where he would be assassinated, Caesar passed the seer and joked, "The ides of March have come," meaning to say that the prophecy had not been fulfilled, to which the seer replied "Aye, Caesar; but not gone." This meeting is famously dramatised in William Shakespeare's play Julius Caesar, when Caesar is warned by the soothsayer to "beware the Ides of March." The Roman biographer Suetonius identifies the "seer" as a haruspex named Spurinna.
Caesar's death was a closing event in the crisis of the Roman Republic, and triggered the civil war that would result in the rise to sole power of his adopted heir Octavian (later known as Augustus). Writing under Augustus, Ovid portrays the murder as a sacrilege, since Caesar was also the Pontifex Maximus of Rome and a priest of Vesta. On the anniversary of Caesar's death in 40 BC, after achieving a victory at the siege of Perugia, Octavian executed 300 senators and knights who had fought against him under Lucius Antonius, the brother of Mark Antony. The executions were one of a series of actions taken by Octavian to avenge Caesar's death. Suetonius and the historian Cassius Dio characterise the slaughter as like a religious sacrifice, noting that it occurred on the Ides of March at the new altar to the deified Julius.
- "Forum in Rome" entry in Oxford Encyclopedia of Ancient Greece and Rome (Oxford University Press, 2010), p. 215.
- H.H. Scullard, Festivals and Ceremonies of the Roman Republic (Cornell University Press, 1981), pp. 42–43.
- Scullard, Festivals and Ceremonies of the Roman Republic, p. 43.
- Scullard, Festivals and Ceremonies of the Roman Republic, p. 90.
- John Lydus (6th century), De mensibus4.36. Other sources place it on 14 March.
- Michele Renee Salzman, On Roman Time: The Codex-Calendar of 354 and the Rhythms of Urban Life in Late Antiquity (University of California Press, 1990), pp. 124 and 128–129; William Warde Fowler, The Roman Festivals of the Period of the Republic (London, 1908), pp. 44–50.
- Maria Grazia Lancellotti, Attis, Between Myth and History: King, Priest, and God (Brill, 2002), p. 81; Bertrand Lançon, Rome in Late Antiquity (Routledge, 2001), p. 91; Philippe Borgeaud, Mother of the Gods: From Cybele to the Virgin Mary, translated by Lysa Hochroth (Johns Hopkins University Press, 2004), pp. 51, 90, 123, 164.
- Gary Forsythe, Time in Roman Religion: One Thousand Years of Religious History (Routledge, 2012), p. 88; Lancellotti, Attis, Between Myth and History, p. 81.
- Michele Renee Salzman, On Roman Time: The Codex Calendar of 354 and the Rhythms of Urban Life in Late Antiquity (University of California Press, 1990), p. 166.
- Jaime Alvar, Romanising Oriental Gods: Myth, Salvation and Ethics in the Cults of Cybele, Isis and Mithras, translated by Richard Gordon (Brill, 2008), p. 288–289.
- Firmicus Maternus, De errore profanarum religionum, 27.1; Rabun Taylor, "Roman Oscilla: An Assessment", RES: Anthropology and Aesthetics 48 (Autumn 2005), p. 97.
- Lydus, De Mensibus 4.59; Suetonius, Otho 8.3; Forsythe, Time in Roman Religion, p. 88.
- Forsythe, Time in Roman Religion, p. 88.
- Macrobius, Saturnalia 1.21.10; Forsythe, Time in Roman Religion, p. 88; Salzman, On Roman Time, p. 168..
- Plutarch, Parallel Lives, Caesar 63
- "William Shakespeare, Julius Caesar, Act 1, Scene II". The Literature Network. Jalic, Inc. 2010. Retrieved 15 March 2010.
- "William Shakespeare, Julius Caesar, Act 3, Scene I". The Literature Network. Jalic, Inc. 2010. Retrieved 15 March 2010.
- Suetonius, Divus Julius 81.
- "Forum in Rome," Oxford Encyclopedia of Ancient Greece and Rome, p. 215.
- Ovid, Fasti 3.697–710; A.M. Keith, entry on "Ovid," Oxford Encyclopedia of Ancient Greece and Rome, p. 128; Geraldine Herbert-Brown, Ovid and the Fasti: An Historical Study (Oxford: Clarendon Press, 1994), p. 70.
- Melissa Barden Dowling, Clemency and Cruelty in the Roman World (University of Michigan Press, 2006), pp. 50–51; Arthur Keaveney, The Army in the Roman Revolution (Routledge, 2007), p. 15.
- Suetonius, Life of Augustus 15.
- Cassius Dio 48.14.2.
- Plutarch, The Parallel Lives, The Life of Julius Caesar
- Nicolaus of Damascus, Life of Augustus (translated by Clayton M. Hall)