Editing Roman calendar (section)

==Months==
The names of Roman months originally functioned as adjectives (e.g., the January kalends occur in the January month) before being treated as substantive nouns in their own right (e.g., the kalends of January occur in January). Some of their etymologies are well-established: January and March honor the gods [[Janus (god)|Janus]]<ref>{{citation |contribution=January, ''n.'' |title=OED }}.</ref> and [[Mars (god)|Mars]];<ref>{{citation |contribution=March, ''n.<sup>2</sup>'' |title=OED }}.</ref> July and August honor [[Julius Caesar]]<ref>{{citation |contribution=July, ''n.'' |title=OED }}.</ref> and his successor, the [[list of Roman emperors|emperor]] [[Augustus]];<ref>{{citation |contribution=August, ''n.'' |title=OED }}.</ref> and the months Quintilis,<ref>{{citation |contribution=†quintile, ''n.<sup>2</sup>'' |title=OED }}.</ref> Sextilis,<ref>{{citation |contribution=sextile, ''adj.'' and ''n.'' |title=OED }}.</ref> September,<ref name=septime>{{citation |contribution=September, ''n.'' |title=OED }}.</ref> October,<ref>{{citation |contribution=October, ''n.'' |title=OED }}.</ref> November,<ref>{{citation |contribution=November, ''n.'' |title=OED }}.</ref> and December<ref>{{citation |contribution=December, ''n.'' |title=OED }}.</ref> are archaic adjectives formed from the [[ordinal numeral|ordinal number]]s from {{nowrap|5 to 10}}, their position in the calendar when it began around the spring equinox in March.<ref name=septime/> Others are uncertain. February may derive from the [[Lupercalia|Februa festival]] or its eponymous ''{{lang|la|februa}}'' ("purifications, expiatory offerings"), whose name may be either [[Sabine language|Sabine]] or preserve an archaic word for [[sulphur]]ic.<ref>{{citation |contribution=February, ''n.'' |title=OED }}.</ref> April may relate to the [[Etruscans|Etruscan]] goddess Apru or the verb ''{{lang|la|aperire}}'' ("to open").{{citation needed|date=March 2017}} May and June may honor [[Maia (goddess)|Maia]]<ref>{{citation |contribution=May, ''n.<sup>2</sup>'' |title=OED }}.</ref> and [[Juno (goddess)|Juno]]<ref>{{citation |contribution=June, ''n.'' |title=OED }}.</ref> or derive from archaic terms for "senior" and "junior". A few [[list of Roman emperors|emperors]] attempted to add themselves to the calendar after Augustus, but without enduring success.

In classical Latin, the days of each month were usually reckoned as:<ref name=perdedor/>

{| class="wikitable" style="white-space: nowrap;" 
|+ Days of the month in the Roman Calendar 
!! colspan=3 style="text-align:right;" | Days in month !! 31d !! 31d !! 30d !! 29d !! 28d
|- style="vertical-align:top;line-height:90%" 
!! colspan=3 style="text-align:right;" | <br>Months before Julian reform !! <small>{{nobold|Mar<br>May<br>Jul<br>Oct}}</small> !! !! !! <small>{{nobold|Jan Apr<br>Jun Aug<br>Sep Nov<br>Dec}}</small> !! <small>{{nobold|Feb}}</small>
|- style="vertical-align:top;line-height:90%" 
!! colspan=3 style="text-align:right;" | <br>Months after Julian reform !! <small>{{nobold|Mar<br>May<br>Jul<br>Oct}}</small> !! <small>{{nobold|Jan<br>Aug<br>Dec}}</small> !! <small>{{nobold|Apr<br>Jun<br>Sep<br>Nov}}</small> !! <small>{{nobold|(Feb)}}</small> !! <small>{{nobold|Feb}}</small>
|- 
! Day name in English !! Day name in Latin !! Abbr !! {{efn|name=four}}{{efn|The months with 31 days before and after the Julian reform – March, May, Quintilis (July), and October – continued using the old system with their Nones on the 7th and Ides on the 15th, making them different from all other months.}} !! {{efn|The months which changed from 29 to 31 days under the Julian reform – January, Sextilis (August), and December – retained their Nones on the 5th and Ides on the 13th, making them different from the other 31-day months but matching all other months.}} !! {{efn| The months which changed from 29 to 30 days under the Julian reform – April, June, September, and November – retained their Nones on the 5th and Ides on the 13th, making them match all other months except those which had had 31 days before the reform.}} !! {{efn| In leap years late in the imperial period, February was reckoned as a 29 day month with all days lasting 24 hours.}} !! {{efn| In leap years early period after the Julian reform, February had 29 days but was reckoned as a 28 day month by treating the sixth day before the March Kalends as lasting for 48 hours.}}
|- align=center style="background-color:lightblue;" 
|align=right|On the Kalends ||align=right|Kalendis ||align=right|Kal. || 1 || 1 || 1 || 1 || 1
|- align=center style="background-color:lavender;"
|align=right|''The day after the Kalends'' ||align=right|''postridie Kalendas''|| ||''2''||''2''||''2''||''2''|| ''2'' 
|- align=center 
|align=right|The 6th day before the Nones ||align=right|ante diem sextum Nonas ||align=right|a.d. VI Non. || style="background-color:lavender" |2 || &nbsp; || &nbsp; || &nbsp; || &nbsp;
|- align=center 
|align=right|The 5th day before the Nones ||align=right|ante diem quintum Nonas ||align=right|a.d. V Non. || 3 || &nbsp; || &nbsp; || &nbsp; || &nbsp;
|- align=center 
|align=right|The 4th day before the Nones ||align=right|ante diem quartum Nonas ||align=right|a.d. IV Non. || 4 || bgcolor=lavender | 2 || bgcolor=lavender | 2 || bgcolor=lavender | 2 || bgcolor=lavender | 2
|- align=center 
|align=right|The 3rd day before the Nones ||align=right|ante diem tertium Nonas ||align=right|a.d. III Non. || 5 || 3 || 3 || 3 || 3
|- align=center 
|align=right|On the day before the Nones ||align=right|Pridie Nonas ||align=right|Prid. Non. || 6 || 4 || 4 || 4 || 4
|- align=center style="background-color:lightblue;" 
|align=right|On the Nones ||align=right|Nonis ||align=right|Non. || 7 || 5 || 5 || 5 || 5
|- align=center style="background-color:lavender;"
|align=right|''The day after the Nones'' ||align=right|''postridie Nonas''|| ||''8''||''6''||''6''||''6''|| ''6'' 
|- align=center 
|align=right|The 8th day before the Ides ||align=right|ante diem octavum Idus ||align=right|a.d. VIII Eid. || bgcolor=lavender | 8 || bgcolor=lavender | 6 || bgcolor=lavender | 6 || bgcolor=lavender | 6 || bgcolor=lavender | 6
|- align=center 
|align=right|The 7th day before the Ides ||align=right|ante diem septimum Idus ||align=right|a.d. VII Eid. || 9 || 7 || 7 || 7 || 7
|- align=center 
|align=right|The 6th day before the Ides ||align=right|ante diem sextum Idus ||align=right|a.d. VI Eid. || 10 || 8 || 8 || 8 || 8
|- align=center 
|align=right|The 5th day before the Ides ||align=right|ante diem quintum Idus ||align=right|a.d. V Eid. || 11 || 9 || 9 || 9 || 9
|- align=center 
|align=right|The 4th day before the Ides ||align=right|ante diem quartum Idus ||align=right|a.d. IV Eid. || 12 || 10 || 10 || 10 || 10
|- align=center 
|align=right|The 3rd day before the Ides ||align=right|ante diem tertium Idus ||align=right|a.d. III Eid. || 13 || 11 || 11 || 11 || 11
|- align=center 
|align=right|On the day before the Ides ||align=right|Pridie Idus ||align=right|Prid. Eid. || 14 || 12 || 12 || 12 || 12
|- align=center style="background-color:lightblue;" 
|align=right|On the Ides ||align=right|Idibus ||align=right|Eid. || 15 || 13 || 13 || 13 || 13
|- align=center style="background-color:lavender;"
|align=right|''The day after the Ides'' ||align=right|''postridie Idus''|| ||''16''||''14''||''14''||''14''|| ''14'' 
|- align=center 
|align=right|The 19th day before the Kalends ||align=right|ante diem undevicesimum Kalendas ||align=right|{{nowrap|a.d. XIX Kal.}} || &nbsp; || bgcolor=lavender | 14 || &nbsp; || &nbsp; || &nbsp;
|- align=center 
|align=right|The 18th day before the Kalends ||align=right|ante diem duodevicesimum Kalendas ||align=right|{{nowrap|a.d. XVIII Kal.}} || &nbsp; || 15 || bgcolor=lavender | 14 || &nbsp; || &nbsp;
|- align=center 
|align=right|The 17th day before the Kalends ||align=right|ante diem septimum decimum Kalendas ||align=right|{{nowrap|a.d. XVII Kal.}} || bgcolor=lavender | 16 || 16 || 15 || bgcolor=lavender | 14 || &nbsp;
|- align=center 
|align=right|The 16th day before the Kalends ||align=right|ante diem sextum decimum Kalendas ||align=right|a.d. XVI Kal. || 17 || 17 || 16 || 15 || bgcolor=lavender | 14
|- align=center 
|align=right|The 15th day before the Kalends ||align=right|ante diem quintum decimum Kalendas ||align=right|a.d. XV Kal. || 18 || 18 || 17 || 16 || 15
|- align=center 
|align=right|The 14th day before the Kalends ||align=right|ante diem quartum decimum Kalendas ||align=right|a.d. XIV Kal. || 19 || 19 || 18 || 17 || 16
|- align=center 
|align=right|The 13th day before the Kalends ||align=right|ante diem tertium decimum Kalendas ||align=right|a.d. XIII Kal. || 20 || 20 || 19 || 18 || 17
|- align=center 
|align=right|The 12th day before the Kalends ||align=right|ante diem duodecimum Kalendas ||align=right|a.d. XII Kal. || 21 || 21 || 20 || 19 || 18
|- align=center 
|align=right|The 11th day before the Kalends ||align=right|ante diem undecimum Kalendas ||align=right|a.d. XI Kal. || 22 || 22 || 21 || 20 || 19
|- align=center 
|align=right|The 10th day before the Kalends ||align=right|ante diem decimum Kalendas ||align=right|a.d. X Kal. || 23 || 23 || 22 || 21 || 20
|- align=center 
|align=right|The 9th day before the Kalends ||align=right|ante diem nonum Kalendas ||align=right|a.d. IX Kal. || 24 || 24 || 23 || 22 || 21
|- align=center 
|align=right|The 8th day before the Kalends ||align=right|ante diem octavum Kalendas ||align=right|a.d. VIII Kal. || 25 || 25 || 24 || 23 || 22
|- align=center 
|align=right|The 7th day before the Kalends ||align=right|ante diem septimum Kalendas ||align=right|a.d. VII Kal. || 26 || 26 || 25 || 24 || 23
|- align=center 
|align=right|The 6th day before the Kalends ||align=right|ante diem sextum Kalendas ||align=right|a.d. VI Kal. || 27 || 27 || 26 || 25 || 24{{efn|After the Julian reform until late in the imperial period, this day was reckoned to last 48 hours during a leap year.}}
|- align=center 
|align=right|The 5th day before the Kalends ||align=right|ante diem quintum Kalendas ||align=right|a.d. V Kal. || 28 || 28 || 27 || 26 || 25
|- align=center 
|align=right|The 4th day before the Kalends ||align=right|ante diem quartum Kalendas ||align=right|a.d. IV Kal. || 29 || 29 || 28 || 27 || 26
|- align=center 
|align=right|The 3rd day before the Kalends ||align=right|ante diem tertium Kalendas ||align=right|a.d. III Kal. || 30 || 30 || 29 || 28 || 27
|- align=center 
|align=right|On the day before the Kalends ||align=right| Pridie Kalendas ||align=right|Prid. Kal. || 31 || 31 || 30 || 29 || 28
|} 
 
Dates after the ides count forward to the kalends of the next month and are expressed as such. For example, March 19 was expressed as "the 14th day before the April Kalends" (''{{lang|la|a.d. XIV Kal. Apr.}}''), without a mention of March itself. The day after a kalends, nones, or ides was also often expressed as the "day after" (''{{lang|la|postridie}}'') owing to their special status as particularly unlucky "black days".

The anomalous status of the new 31-day months under the Julian calendar was an effect of Caesar's desire to avoid affecting the [[Roman festivals|festivals]] tied to the nones and ides of various months. However, because the dates at the ends of the month all counted forward to the next kalends, they were all shifted by one or two days by the change. This created confusion with regard to certain anniversaries. For instance, [[Augustus]]'s birthday on the 23rd{{spaces}}day of September was ''{{lang|la|a.d. VIII Kal. Oct.}}'' in the old calendar but ''{{lang|la|a.d. IX Kal. Oct.}}'' under the new system. The ambiguity caused honorary festivals to be held on either or both dates.