Maius ormensis Maius (May) was the fifth month of the ancientRoman calendar in the classical period, followingAprilis (April) and precedingIunius (June). On the oldest Roman calendar that had begun with March, it was the third of ten months in the year. May had 31 days.

The Romans considered May an infelicitous month. Although it began with one of the most notoriously licentious holidays of the Roman calendar, the Games of Flora(Ludi Florae), the middle of the month was devoted to propitiating thelemures, the restless shades of the dead.^[1]

The Romans did not number days of a month sequentially from the 1st through the last day. Instead, they counted back from the three fixed points of the month: theNones (5th or 7th, depending on the length of the month), theIdes (13th or 15th), and theKalends (1st) of the following month. Thus the last day of May was thepridie Kalendas Iunias,^[2] "day before the Kalends of June". Roman counting wasinclusive; May 9 wasante diem VII Idūs Maias, "the 7th day before the Ides (15th) of May," usually abbreviateda.d. VII Id. Mai. (or with thea.d. omitted altogether); May 23 wasX Kal. Iun., "the 10th day before the Kalends of June."

On the calendar of theRoman Republic and earlyPrincipate, each day was marked with a letter to denote its religiously lawful status. In May, these were:

• F fordies fasti, days when it was legal to initiate action in the courts ofcivil law;
• C, fordies comitalis, a day on which the Roman people could hold assemblies(comitia), elections, and certain kinds of judicial proceedings;
• N fordies nefasti, when these political activities and the administration of justice were prohibited;
• NP, the meaning of which remains elusive, but which markedferiae, public holidays;
• QRCF (perhaps forquando rex comitiavit fas^[3]), a day when it was religiously permissible for therex (probably the priest known as therex sacrorum) to call for an assembly.^[4]

By the late 2nd century AD, extant calendars no longer show days marked with these letters, probably in part as a result of calendar reforms undertaken byMarcus Aurelius.^[5] Days were also marked withnundinal letters in cycles ofA B C D E F G H, to mark the "market week"^[6] (these are omitted in the table below).

On adies religiosus, individuals were not to undertake any new activity, nor do anything other than tend to the most basic necessities. Adies natalis was an anniversary such as a temple founding or rededication, sometimes thought of as the "birthday" of a deity. During theImperial period, the birthdays and anniversaries of the emperor and his family gained prominence as Roman holidays. After the mid-1st century AD, a number of dates are added to calendars forspectacles and games(ludi) held in honor of various deities in the venue called a "circus"(ludi circenses). After the time ofConstantine, the first emperor to convert to Christianity, sacrifices were omitted from theludi. In the mid-4th century, games celebrating the victories of theConstantinian dynasty were held May 4–9 (theLudi Maximati) and May 13–17(Ludi Persici).^[7]

Festivals marked in large letters on extantfasti, represented by festival names in all capital letters on the table, are thought to have been the most ancient holidays, becoming part of the calendar before 509 BC.^[8] TheAmbarvalia, a "moveable feast"(feriae conceptivae) involving thelustration of the fields, seems to have been held in May, with May 29 commonly the date on which it fell.

Unless otherwise noted, the dating and observances on the following table are fromH. H. Scullard,Festivals and Ceremonies of the Roman Republic (Cornell University Press, 1981), pp. 116–125.

• Floréal
• Rosalia, a rose festival celebrated during the Imperial period at varying times mainly in May

• May
• Months of the Roman calendar

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