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.
Intercalaris -- inter-calendar month
Latin Intercalaris "inter-calendar"
Latin Mercedonius (popular name) "?"
Intercalaris had 27 days until the month was abolished by Julius.
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 days long.
December -- the tenth 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.
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.
Monday is considered either the first or the second day of the week, between Sunday and Tuesday. It gets its name from Mani (Old English Mona), the Germanic Moon god.
Tuesday is considered either the second or the third day of the week, between Monday and Wednesday. The English and Scandinavian names are derived from the Nordic god Tyr (in Old English, Tiw, Tew or Tiu. In Swedish, Tisdag, Danish: Tirsdag, Finnish: Tiistai).
Wednesday is considered either the third or the fourth day of the week, between Tuesday and Thursday. The name comes from the Old English Wodnesdæg meaning the day of the Germanic god Woden who was a god of the Anglo-Saxons in England until about the 7th C. AD.
Thursday, by international standard, is the fourth day of the week, falling between Wednesday and Friday. The name Thursday comes from the Old English Þunresdæg, meaning the day of Þunor, commonly known in Modern English as Thor, the Norse god of thunder. Thor replaced the Roman god of thunder, Jupiter, as the namesake of the fourth day of the week after the Anglo-Saxon invasions of Rome.
Friday is the fifth day of the week, falling between Thursday and Saturday. In countries that adopt a Sunday-first convention, it is commonly considered the sixth day of the week. The name Friday comes from the Old English frigedæg, meaning the day of Frige, the Norse god of beauty. Frige replaced the Roman god of beauty, Venus, as the namesake of the fifth day of the week after the Anglo-Saxon invasions of Britain. This is why the word for Friday in French is Vendredi, and in Italian it is Venerdi, after Venus, while in Modern German it is Freitag.
Saturday is the seventh day of the week, between Friday and Sunday. It is the only day of the week to retain its Roman origin in English, named after the Roman god of time Saturn. Many of the other days of the week adopted names of Saxon gods in Northern Europe. By tradition derived from ancient Jews, Saturday is the last day of the week.
Sunday is considered either the first or the seventh day of the week, between Saturday and Monday, and the second day of the weekend in some cultures. It is considered a holiday in lands of Christian tradition, the day Christians most commonly attend Church (Saturday is the other day that some consider to be the Sabbath). In English, Sunday gets its name from Sunna, or Sunne the Germanic sun goddess. In the Gregorian calendar, no century can start on a Sunday. In the Hebrew calendar, no year can start on a Sunday. Any month beginning on a Sunday will contain a Friday the 13th.