In ancient Roman religion and myth, Janus (/ˈdʒeɪnəs/ JAY-nəs; Latin: Ianvs [ˈi̯aːnʊs]) is the god of beginnings, gates, transitions, time, duality, doorways,[2] passages, frames, and endings.

[16] Interpretations concerning the god's fundamental nature either limit it to this general function or emphasize a concrete or particular aspect of it (identifying him with light,[17] the sun,[18] the moon,[19] time,[20] movement,[21] the year,[22] doorways,[23] bridges,[24] etc.)

[44] Plutarch in his Parallel Lives mention that Numa Pompilius made January the first month in the calendar instead of March by the next reason: "he wished in every case that martial influences should yield precedence to civil and political.

[59] The four-sided structure known as the Arch of Janus in the Forum Transitorium dates from the 1st century of the Christian era: according to common opinion it was built by the Emperor Domitian.

However American scholars L. Ross Taylor and L. Adams Holland on the grounds of a passage of Statius[60] maintain that it was an earlier structure (tradition has it the Ianus Quadrifrons was brought to Rome from Falerii[61]) and that Domitian only surrounded it with his new forum.

Another way of investigating the complex nature of Janus is by systematically analysing his cultic epithets: religious documents may preserve a notion of a deity's theology more accurately than other literary sources.

The manuscript has: Many reconstructions have been proposed:[67] they vary widely in dubious points and are all tentative, nonetheless one can identify with certainty some epithets: The epithets that can be identified are: The above-mentioned sources give: Ianus Geminus, I. Pater, I. Iunonius, I. Consivius, I. Quirinus, I. Patulcius and Clusivius (Macrobius above I 9, 15): Ι. Κονσίβιον, Ι. Κήνουλον, Ι. Κιβουλλιον, I. Πατρίκιον, I. Κλουσίβιον, I. Ιουνώνιον, I. Κυρινον, I. Πατούλκιον, I. Κλούσιον, I. Κουριάτιον (Lydus above IV 1); I. Κιβούλλιον, I. Κυρινον, I. Κονσαιον, I. Πατρίκιον (Cedrenus Historiarum Compendium I p. 295 7 Bonn); I. Clusiuius, I. Patulcius, I. Iunonius, I. Quirinus (Servius Aen.

[84] The origin of this epithet might be either concrete, referring directly to the image of the god reproduced on coins[85] and supposed to have been introduced by king Numa in the sanctuary at the lowest point of the Argiletum,[86] or to a feature of the Ianus of the Porta Belli, the double gate ritually opened at the beginning of wars,[87] or abstract, deriving metaphorically from the liminal, intermediary functions of the god themselves: both in time and space passages connected two different spheres, realms or worlds.

[88] The Janus quadrifrons or quadriformis, brought according to tradition from Falerii in 241 BC[89] and installed by Domitian in the Forum Transitorium,[90] although having a different meaning, seems to be connected to the same theological complex, as its image purports an ability to rule over every direction, element and time of the year.

[95] The antithetical quality of the two epithets is meant to refer to the alterning opposite conditions[96] and is commonly found in the indigitamenta: in relation to Janus, Macrobius cites instances of Antevorta and Postvorta,[97] the personifications of two indigitations of Carmentis.

[100] Poets tried to explain this rite by imagining that the gate closed either war or peace inside the ianus, but in its religious significance it might have been meant to propitiate the return home of the victorious soldiers.

[102] Other scholars, mainly Germanophone, think it is related on the contrary to the martial character of the god Quirinus, an interpretation supported by numerous ancient sources: Lydus,[103] Cedrenus,[104] Macrobius,[105] Ovid,[106] Plutarch[107] and Paul the Daecon.

[112] Koch on the other hand sees the epithet Janus Quirinus as a reflection of the god's patronage over the two months beginning and ending the year, after their addition by king Numa in his reform of the calendar.

Capdeville considers Cedrenus' text to be due to a paleographic error: only Coenulus is indubitably an epithet of Janus and the adjective used to explain it, meaning to present and to treat well at dinner, was used in a ritual invocation before meals, wishing the diners to make good flesh.

Festus and other ancient authors[132] explain Curiatius by the aetiological legend of the Tigillum: the expiation undergone by P. Horatius after his victory over the Alban Curiatii for the murder of his own sister, by walking under a beam with his head veiled.

[144] The flamen of Portunus performed the ritual greasing of the spear of the god Quirinus on 17 August, day of the Portunalia, on the same date that the temple of Janus in the Forum Holitorium had been consecrated by consul Gaius Duilius in 260 BC.

[146] For the same reason everybody devoted a short time to his usual business,[147] exchanged dates, figs and honey as a token of well wishing and made gifts of coins called strenae.

[151] This libum was named ianual and it was probably correspondent to the summanal offered the day before the Summer solstice to god Summanus, which however was sweet being made with flour, honey and milk.

[159][160] Adams Holland opines it would have been originally the name of a small bridge connecting the Tiber Island (on which she supposes the first shrine of Janus stood) with the right bank of the river.

[179] The rite of the opening and closure of the Janus Quirinus would thus reflect the idea of the reintegration of the miles into civil society, i.e. the community of the quirites, by playing a lustral role similar to the Tigillum Sororium and the porta triumphalis located at the south of the Campus Martius.

[184] The rite and myth have been interpreted by Dumezil as a purification and desacralization of the soldiers from the religious pollution contracted in war, and a freeing of the warrior from furor, wrath, as dangerous in the city as it is necessary on campaign.

Carna was a nymph of the sacred lucus of Helernus, made goddess of hinges by Janus with the name of Cardea, and had the power of protecting and purifying thresholds and the doorposts.

Consequently, the association of both Janus and the god Helernus with Carna-Crane is highlighted in this myth: it was customary on that day to eat ivetch (mashed beans) and lard, which were supposed to strengthen the body.

Cardea had also magic powers for protecting doorways (by touching thresholds and posts with wet hawthorn twigs) and newborn children by the aggression of the striges (in the myth the young Proca).

Janus would have also effected the miracle of turning the waters of the spring at the foot of the Viminal from cold to scorching hot to fend off the assault of the Sabines of king Titus Tatius, come to avenge the kidnapping of their daughters by the Romans.

[217] The uniqueness of Janus in Latium has suggested to L. Adams Holland and J. Gagé the hypothesis of a cult brought from far away by sailors and strictly linked to the amphibious life of the primitive communities living on the banks of the Tiber.

[241] On the other hand, as expected Janus is present in region I of Martianus Capella's division of Heaven and in region XVI, the last one, are to be found the Ianitores terrestres (along with Nocturnus), perhaps to be identified in Forculus, Limentinus and Cardea,[242] deities strictly related to Janus as his auxiliaries (or perhaps even no more than concrete subdivisions of his functions) as the meaning of their names implies: Forculus is the god of the forca, a iugum, low passage, Limentinus the guardian of the limes, boundary, Cardea the goddess of hinges, here of the gates separating Earth and Heaven.

[256] William Betham argued that the cult arrived from the Middle East and that Janus corresponds to the Baal-ianus or Belinus of the Chaldeans, sharing a common origin with the Oannes of Berosus.

His abode is at the limits of Earth, at the extremity of Heaven; he is the protector of the gods; his birth is at the beginning of time; he is the forefather of mankind, the generator of classes and the founder of the social order.

In Cassandra Clare's The Shadowhunter Chronicles, the counterpart of Jace Herondale from an alternate dimension called Thule chooses the name "Janus" for himself after the Roman god.