• Middle English sone(n)day or sun(nen)day
• Old English sunnandæg “day of the sun”
• Germanic sunnon-dagaz “day of the sun”
• Latin dies solis “day of the sun”
• Ancient Greek hemera heli(o)u, “day of the sun”

• Middle English monday or mone(n)day
• Old English mon(an)dæg “day of the moon”
• Latin dies lunae “day of the moon”
• Ancient Greek hemera selenes “day of the moon”

• Middle English tiwesday or tewesday
• Old English tiwesdæg “Tiw's (Tiu's) day”
• Latin dies Martis “day of Mars”
• Ancient Greek hemera Areos “day of Ares”

Tiu (Twia) is the English/Germanic god of war and the sky. He is identified with the Norse god Tyr.

Mars is the Roman god of war.

Ares is the Greek god of war.

• Middle English wodnesday, wednesday, or wednesdai
• Old English wodnesdæg “Woden's day”
• Latin dies Mercurii “day of Mercury”
• Ancient Greek hemera Hermu “day of Hermes”

Woden is the chief Anglo-Saxon/Teutonic god. Woden is the leader of the Wild Hunt. Woden is from wod “violently insane” + -en “headship”. He is identified with the Norse Odin.

Mercury is the Roman god of commerce, travel, theivery, eloquence and science. He is the messenger of the other gods.

Hermes is the Greek god of commerce, invention, cunning, and theft. He is the messenger and herald of the other gods. He serves as patron of travelers and rogues, and as the conductor of the dead to Hades.

• Middle English thur(e)sday
• Old English thursdæg
• Old Norse thorsdagr “Thor's day”
• Old English thunresdæg “thunder's day”
• Latin dies Jovis “day of Jupiter”
• Ancient Greek hemera Dios “day of Zeus”.

Thor is the Norse god of thunder. He is represented as riding a chariot drawn by goats and wielding the hammer Miölnir. He is the defender of the Aesir, destined to kill and be killed by the Midgard Serpent.

Jupiter (Jove) is the supreme Roman god and patron of the Roman state. He is noted for creating thunder and lightning.

Zeus is Greek god of the heavens and the supreme Greek god.

• Middle English fridai
• Old English frigedæg “Freya's day” composed of Frige (genetive singular of Freo) + dæg “day” (most likely) or composed of Frig “Frigg” + dæg “day” (least likely)
• Germanic frije-dagaz “Freya's (or Frigg's) day”
• Latin dies Veneris “Venus's day”
• Ancient Greek hemera Aphrodites “day of Aphrodite”

Freo is identical with freo, meaning free. It is from the Germanic frijaz meaning “beloved, belonging to the loved ones, not in bondage, free”.

Freya (Fria) is the Teutonic goddess of love, beauty, and fecundity (prolific procreation). She is identified with the Norse god Freya. She is leader of the Valkyries and one of the Vanir. She is confused in Germany with Frigg.

Frigg (Frigga) is the Teutonic goddess of clouds, the sky, and conjugal (married) love. She is identified with Frigg, the Norse goddess of love and the heavens and the wife of Odin. She is one of the Aesir. She is confused in Germany with Freya.

Venus is the Roman goddess of love and beauty.

Aphrodite (Cytherea) is the Greek goddess of love and beauty.

• Middle English saterday
• Old English sæter(nes)dæg “Saturn's day”
• Latin dies Saturni “day of Saturn”
• Ancient Greek hemera Khronu “day of Cronus”

Saturn is the Roman and Italic god of agriculture and the consort of Ops. He is believed to have ruled the earth during an age of happiness and virtue.

Cronus (Kronos, Cronos) is the Greek god (Titan) who ruled the universe until dethroned by his son Zeus.

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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• Middle English octobre
• Latin October
• Latin octo “eight” + -ber (adj. suffix)
• Latin october mensis “eighth month”

October has always had 31 days.

• 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.

• 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.