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Beginners' Latin
Thomas Becket, Archbishop of Canterbury, pictogram. c.1282-92. Cat ref: E 36/274 f 295. Crown copyright

Dating Latin documents




Roman numerals

Months of the year

Days of the week





Between 1086 and 1733, a variety of methods were used to date Latin documents.
This page will give you a basic introduction to these methods.
We will look at

  • Numbers
  • Dates
  • Roman numerals
  • Months
  • Days of the week
  • Feasts
  • Octave

Remember that this is not a definitive guide.
If you would like to look at dating documents in more detail, C.R. Cheney and M. Jones (eds), A Handbook of Dates: for students of British history (Cambridge University Press, revd 2000) is the standard reference work.



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When numbers are written in full, they are given in these forms.

Latin English Latin English
unus, -a, -um   one primus, -a, -um first
duo, due, duo two secundus second
tres, tria three tertius third
quattuor four quartus fourth
quinque five quintus fifth
sex six sextus sixth
septem seven septimus seventh
octo eight octavus eighth
novem nine nonus ninth
decem  ten decimus tenth
undecim eleven undecimus eleventh
duodecim twelve duodecimus twelfth
tredecim thirteen tertius decimus thirteenth
quattuordecim fourteen quartus decimus fourteenth
quindecim fifteen quintus decimus fifteenth
sedecim sixteen sextus decimus sixteenth
septemdecim seventeen septimus decimus seventeenth
duodeviginti eighteen duodevicesimus eighteenth
undeviginti nineteen undevicesimus nineteenth
viginti twenty vicesimus twentieth
viginti unus twenty one vicesimus primus twenty first
viginti duo twenty two vicesimus secundus twenty second
viginti tres twenty three vicesimus tertius twenty third
viginti quartus twenty four vicesimus quartus twenty fourth
viginti quintus twenty five vicesimus quintus twenty fifth
viginti sex twenty six vicesimus sextus twenty sixth
viginti septem twenty seven vicesimus septimus twenty seventh
viginti octo twenty eight vicesimus octavus twenty eighth
viginti novem twenty nine vicesimus nonus twenty ninth
triginta thirty tricesimus thirtieth
quadraginta forty quadragesimus fortieth
quinquaginta fifty quinquagesimus fiftieth
sexaginta sixty sexagesimus sixtieth
septuaginta seventy septuagesimus seventieth
octoginta eighty octogesimus eightieth
nonaginta ninety nonagesimus ninetieth
centum one hundred centesimus one hundreth
centum et unus one hundred and one centesimus primus one hundred and first
ducenti, -ae, -a two hundred ducentesimus two hundredth
trecenti three hundred trecentesimus three hundredth
quadringenti four hundred quadringentesimus four hundredth
quingenti five hundred quingentesimus five hundredth
sescenti six hundred sescentesimus six hundredth
septingenti seven hundred septingentesimus seven hundredth
octingenti eight hundred octingentesimus eight hundredth
nongenti nine hundred nongentesimus nine hundredth
mille one thousand millesimus thousanth

Don’t feel that you have to learn them all at once.

If you know any French or Italian, can you see any similarities with the numbers in these languages?

handy Handy Hints  
  1. Keep looking for patterns when you read through the numbers.
    If you understand how the words are made up, you are more likely to remember them.
  2. Can you see any similarities with English numbers or dates? For example
  •  September is our seventh month (septem means seven)
  •  The decimal system is based on units of ten (decem means ten)

Remember that a few numbers decline

  • unus, -a, -um
  • duo, due, duo
  • tres, tria
  • ducenti, -ae, -a two hundred declines like novus, -a, -um


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Dates are expressed using ‘first’, ‘second’, ‘third’, rather than ‘one’, ‘two’, ‘three’. These are always in the ablativeGlossary - opens in a new window case. Generally, the ‘us’ ending becomes an ‘o’.

secundo on the second
centesimo primo die on the hundred and first day
anno regni regis Johannis filii regis Henrici sexagesimo in the sixtieth year of the reign of King John son of King Henry
anno domini millesimo ducentesimo quinto decimo in the year of our Lord one thousand two hundred and fifteen (or, 1215 AD)

Roman numerals

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Numbers were expressed in Roman numeralsGlossary - opens in a new window throughout the period covered by this tutorial.

Arabic numerals ('1', '2', '3' etc.) were also used in England from the sixteenth century onwards.

In Latin documents, Roman numerals were often written in lower case, rather than in capital letters. If a number ended in an 'i', this was often written as a 'j'.

Classic Roman numerals Roman numerals in medieval Latin documents
I = 1 i or j = 1
II = 2 ii or ij = 2
IV = 4 iiii or iiij = 4 (not usually iv)
V = 5 V or v = 5
X = 10 X or x = 10
XL = 40 xl = 40 A smaller numeral in front of a larger numeral indicates subtraction.
L = 50 l = 50 Don’t confuse this with ‘i’.
LX = 60 lx = 60 A larger numeral in front of a smaller numeral indicates addition.
C = 100 C = 100
D = 500 D = 500
M = 1000 M = 1000

Months of the year

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menses anni mensis, -is (m.) month


Latin word and English meaning ‘month of ...’
Januarius, -i (m.) January mensis Januarii
Februarius, -i (m.) February mensis Februarii
Martius, -i (m.) March mensis Martii
Aprilis, Aprilis (m.) April mensis Aprilis
Maius, -i (m.) May mensis Maii
Junius, -i (m.) June mensis Junii
Julius, -i (m.) July mensis Julii
Augustus, -i (m.) August mensis Augusti
September, Septembris (m.) September mensis Septembris
October, Octobris (m.) October mensis Octobris
November, Novembris (m.) November mensis Novembris
December, Decembris (m.) December mensis Decembris


decimo Januarii on the tenth of January
tricesimo primo Decembris on the thirty first of December
vicesimo octavo die mensis Augusti on the twenty eighth day of the month of August

Days of the week

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dies septimane septimana, -e (f.) week


dies Lune Monday
dies Martis Tuesday
dies Mercurii Wednesday
dies Iovis Thursday
dies Veneris Friday
dies Sabbati Saturday
dies Dominica Sunday


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As medieval England was a CatholicGlossary - opens in a new window country, a large number of religious feast days were celebrated. Many feasts related to a particular saintGlossary - opens in a new window. These feasts were often used to date events.

For example, a charter might have been granted

in festo sancti Edwardi martiris on the feast of Saint Edward the MartyrGlossary - opens in a new window
festum, -i (n.) feast
martir, martiris (m.) martyrGlossary - opens in a new window


in vigilia festi on the eve of the feast vigilia, -e (f.) eveGlossary - opens in a new window
in crastino festi on the morrow of the feast crastinum, -i (n.) morrowGlossary - opens in a new window

Events were also dated

ad festum on the feast
ante festum before the feast
apud festum at the feast
post festum after the feast

For example

ad festum sancti Johannis baptiste at the feast of Saint John the BaptistGlossary - opens in a new window
apud festum beati Thome martiris at the feast of the Blessed Thomas the MartyrGlossary - opens in a new window
beatus, -a, -um (m.) blessed Thomas, -e (m.) Thomas
ante festum sancte Marie virginis before the feast of Saint Mary the Virgin
virgo, virginis (f.) virgin

A list of the main feasts, with the calendar dates that they correspond to, is given in C.R. Cheney and M. Jones (eds), A Handbook of Dates: for students of British history (Cambridge University Press, revd 2000).


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An octaveGlossary - opens in a new window is a period of eight days inclusive.

octaba, -e (f.) octave
octava, -e (f.) octave

You will often see this term used in dates.
For example

in octava festi sancti Michaelis on the octave of the feast of Saint MichaelGlossary - opens in a new window
Michael, Michaelis (m.) Michael

The feast of Saint Michael is on 29 September. Therefore, the octave of the feast is a period of eight days inclusive later: 6 October.

The table below shows you how to calculate the octave of Saint Michael. You can use the same principle to calculate the octave of any feast.

Feast Calendar date Day number
Saint Michael 29 September 1
  30 September 2
  1 October 3
  2 October 4
  3 October 5
  4 October 6
  5 October 7
octave of the feast of Saint Michael 6 October 8