HISTORY OF THE ORIGIN OF THE DAYS AND THE MONTHS

Origin of the Days
The names of the days of the week in Spanish and English don't seem very much alike. But in fact they have similar origins. Surprisingly, however, the day with the names in the two languages sounding the most alike — Saturday in English and sábado in Spanish — has names that aren't connected.

The etymology (word history) of most of the days the week are linked to Roman mythology. The Romans saw a connection between their gods and the changing face of the nighttime sky, so it became natural to use their gods' names for the planets — the ones they were able to track in the sky were Mercury, Venus, Mars, Jupiter and Saturn. Those five planets plus the moon and sun made seven major astronomical bodies, so when the seven-day week was imported from Mesopotamia early in the fourth century it was a natural to use those astronomical names for the days of the week.

Eventually, the first day of the week was named after the sun, followed by the moon, Mars, Mercury, Jupiter, Venus and Saturn. The names of the week were adopted with little change throughout most of the Roman Empire and even beyond. In only a few cases were changes made.

In Spanish, the five weekdays all retained their planetary names. Those are the five days whose names end in -es, a shortening of the Latin word for "day," dies. Thus lunes comes from the word for moon (luna), and the planetary connection is also apparent with martes (Mars, Tuesday), miércoles (Mercury, Wednesday) and viernes (Venus, Friday).

The connection with Jupiter is not quite so apparent with jueves, the word for Thursday, until you remember that "Jovian" is the adjective form of Jupiter in English, coming from a Latin root.

In Spanish, that leaves the words for Saturday and Sunday that weren't adopted using the Roman naming pattern. Domingo, the word for Sunday, comes from a Latin word meaning "Lord's day." And sábado, the word for Saturday, comes from the Hebrew word Sabbath, meaning a day of rest (in Jewish and Christian tradition, God rested on the seventh day of creation).

In English, the pattern is similar, but with a key difference. The connections between Sunday and the sun, between Monday and the moon, and between Saturn and Saturday should be obvious. The difference with the other days is that English is a Germanic language, and the names of equivalent Germanic gods were substituted for the Roman gods.

Mars, for example, was the god of war, while the Germanic god of war was Tiu, whose name became part of Tuesday. Wednesday is a modification of Woden's Day; Woden was a god who was swift like Mercury. You may have heard of the Norse god Thor; a variation of that name was the basis for naming Thursday. Finally, Frigg, after whom Friday was named, was like Venus a goddess of love.

Origin of the Months

The original Roman year had 10 named months Martius "March", Aprilis "April", Maius "May", Junius "June", Quintilis "July", Sextilis "August", September "September", October "October", November "November", December "December", and probably two unnamed months in the dead of winter when not much happened in agriculture. The year began with Martius "March". Numa Pompilius, the second king of Rome circa 700 BC, added the two months Januarius "January" and Februarius "February". He also moved the beginning of the year from Marius to Januarius and changed the number of days in several months to be odd, a lucky number. After Februarius there was occasionally an additional month of Intercalaris "intercalendar". This is the origin of the leap-year day being in February. In 46 BC, Julius Caesar reformed the Roman calendar (hence the Julian calendar) changing the number of days in many months and removing Intercalaris.

January -- Janus’s month
Middle English Januarie
Latin Januarius "of Janus"
Latin Janu(s) "Janus" + -arius "ary (pertaining to)"
Latin Januarius mensis "month of Janus"

Janus is the Roman god of gates and doorways, depicted with two faces looking in opposite directions. His festival month is January.

Januarius had 29 days, until Julius when it became 31 days long.

February -- month of Februa
Middle English Februarius
Latin Februarius "of Februa"
Latin Februa(s) "Februa" + -arius "ary (pertaining to)"
Latin Februarius mensis "month of Februa"
Latin dies februatus "day of purification"

Februarius had 28 days, until circa 450 BC when it had 23 or 24 days on some of every second year, until Julius when it had 29 days on every fourth year and 28 days otherwise.

Februa is the Roman festival of purification, held on February fifteenth. It is possibly of Sabine origin.

March -- Mars’ month
Middle English March(e)
Anglo-French March(e)
Old English Martius
Latin Martius "of Mars"
Latin Marti(s) "Mars" + -us (adj. suffix)
Latin Martius mensis "month of Mars"

Martius has always had 31 days.

March was the original beginning of the year, and the time for the resumption of war.

Mars is the Roman god of war. He is identified with the Greek god
Ares.

April -- Aphrodite’s month
Old English April(is)
Latin Aprilis
Etruscan Apru
Greek Aphro, short for Aphrodite.

Aprilis had 30 days, until Numa when it had 29 days, until Julius when it became 30 days long.

Aphrodite is the Greek goddess of love and beauty. She is identified with the Roman goddess Venus.

May -- Maia’s month
Old French Mai
Old English Maius
Latin Maius "of Maia"
Latin Maius mensis "month of Maia"

Maius has always had 31 days.

Maia (meaning "the great one") is the Italic goddess of spring, the daughter of Faunus, and wife of Vulcan.

June -- Juno’s month
Middle English jun(e)
Old French juin
Old English junius
Latin Junius "of Juno"
Latin Junius mensis "month of Juno"

Junius had 30 days, until Numa when it had 29 days, until Julius when it became 30 days long.

Juno is the principle goddess of the Roman Pantheon. She is the goddess of marriage and the well-being of women. She is the wife and sister of Jupiter. She is identified with the Greek goddess
Hera.

July -- Julius Caesar’s month
Middle English Julie
Latin Julius "Julius"
Latin Julius mensis "month of Julius"
Latin quintilis mensis "fifth month"

Quintilis (and later Julius) has always had 31 days.

Julius Caesar reformed the Roman calendar (hence the Julian calendar) in 46 BC. In the process, he renamed this month after himself.

August -- Augustus Caesar’s month
Latin Augustus "Augustus"
Latin Augustus mensis "month of Augustus"
Latin sextilis mensis "sixth month"

Sextilis had 30 days, until Numa when it had 29 days, until Julius when it became 31 days long.

Augustus Caesar clarified and completed the calendar reform of Julius Caesar. In the process, he also renamed this month after himself.

September -- the seventh month
Middle English septembre
Latin September
Latin septem "seven" + -ber (adj. suffix)
Latin september mensis "seventh month"

September had 30 days, until Numa when it had 29 days, until Julius when it became 30 days long.

October -- the eighth month
Middle English octobre
Latin October
Latin octo "eight" + -ber (adj. suffix)
Latin october mensis "eighth month"

October has always had 31 days.

November -- the nineth month
Middle English Novembre
Latin November
Latin Novembris mensis "nineth month"

Novembris had 30 days, until Numa when it had 29 days, until Julius when it became 30 dayslong.

December -- the 10th month
Middle English decembre
Old French decembre
Latin december "tenth month"
Latin decem "ten" + -ber (adj. suffix)

December had 30 days, until Numa when it had 29 days, until Julius when it became 31 days long.