Huit jours and quinze jours are French time phrases meaning “a week” and “a fortnight” respectively. Literally they translate as “eight days” and “fifteen days,” but in practice they refer to seven and fourteen days. The mismatch is a long-standing feature of the language, with roots in Roman methods of counting and in legal and religious usage.

Literal and figurative meaning

Huit jours literally means “eight days.” Figuratively, it means “a week” or “seven days.” Quinze jours literally means “fifteen days.” Figuratively, it means “two weeks” or “a fortnight.” The extra day in each count reflects the old habit of including the starting day in a period, so a week counted from Monday to Monday became eight days, and two weeks became fifteen.

Why eight and fifteen

The Romans divided the month into periods of varying length. One common division was a period of eight days followed by a period of seven days, repeated twice to make a month. This gave a “fortnight” of fifteen days. The Romans also counted inclusively, treating the current day as the first day of any period. A week that began on Monday and ended on the following Monday was therefore counted as eight days.

Legal and religious usage reinforced the pattern. In medieval French, sous huitaine and sous quinzaine were set legal deadlines meaning “within eight days” and “within fifteen days” exactly, not approximately. The liturgical calendar also used la quinzaine de Pâques to refer to the fifteen days from Palm Sunday to the Sunday after Easter.

Usage examples with huit jours

• Je pars dans huit jours. – “I am leaving in a week.”
• Il est revenu il y a huit jours. – “He came back a week ago.”
• La grippe dure environ huit jours. – “The flu lasts about a week.”
• Elle a donné ses huit jours à son employeur. – “She gave her employer a week’s notice.”
• Nous nous voyons tous les huit jours. – “We see each other every week.”
• Le colis arrivera dans huit jours. – “The parcel will arrive in a week.”
• Il a pris huit jours de vacances. – “He took a week’s holiday.”
• Je lui ai donné ses huit jours. – “I gave him a week’s notice” (dismissed him).
• Dimanche en huit, nous dînons chez eux. – “A week from Sunday, we are having dinner at their place.”
• La réparation prendra huit jours. – “The repair will take a week.”

Usage examples with quinze jours

• Je reviens dans quinze jours. – “I will be back in a fortnight.”
• Elle part en vacances quinze jours. – “She is going on holiday for a fortnight.”
• Nous nous réunissons tous les quinze jours. – “We meet every fortnight.”
• Il y a quinze jours, j’ai vu Marie. – “A fortnight ago, I saw Marie.”
• Le projet prendra quinze jours. – “The project will take a fortnight.”
• Elle va chez le coiffeur tous les quinze jours. – “She goes to the hairdresser every fortnight.”
• Les résultats seront publiés dans quinze jours. – “The results will be published in a fortnight.”
• Il a passé quinze jours à Lyon. – “He spent a fortnight in Lyon.”
• Nous avons quinze jours pour répondre. – “We have a fortnight to reply.”
• La formation dure quinze jours. – “The training lasts a fortnight.”

Related expressions

Une huitaine is a feminine noun meaning “about a week” or “a week.” It is slightly more formal or approximate than huit jours. Une quinzaine is a feminine noun meaning “about a fortnight” or “two weeks.” Both are used in legal, administrative and everyday contexts.

• Dans une huitaine de jours – “In about a week.”
• Dans une quinzaine de jours – “In about a fortnight.”
• Sous huitaine – “Within a week” (legal).
• Sous quinzaine – “Within a fortnight” (legal).
• À huitaine – “A week from now” (legal).
• À quinzaine – “A fortnight from now” (legal).
• Tous les huit jours – “Every week.”
• Tous les quinze jours – “Every fortnight.”
• Donner ses huit jours – “To give a week’s notice” or “to dismiss someone with a week’s notice.”
• Une quinzaine de personnes – “About fifteen people” (note: here quinzaine means an approximate count of fifteen, not a fortnight).

Synonyms and alternatives

French alternatives for “a week”:

• Une semaine – “A week.”
• Une huitaine – “About a week” or “a week.”
• Sept jours – “Seven days.”

French alternatives for “a fortnight”:

• Deux semaines – “Two weeks.”
• Une quinzaine – “About a fortnight” or “two weeks.”
• Quatorze jours – “Fourteen days” (rare in practice).

English equivalents:

• “A week” for huit jours.
• “A fortnight” for quinze jours.
• “Two weeks” for quinze jours.

Register and tone

Both phrases are neutral and common in everyday French. Huit jours and quinze jours are used in speech and writing alike. Une huitaine and une quinzaine are slightly more formal. Sept jours and quatorze jours are possible but rare; French speakers almost always use huit and quinze for these durations. The English word “fortnight” is the closest equivalent to quinze jours, though it is less common in Australian English than “two weeks.”

Summary

Huit jours and quinze jours literally mean “eight days” and “fifteen days” but in practice mean “a week” and “a fortnight.” The extra day comes from Roman counting methods, which included the starting day in a period, and from old month divisions of eight and seven days. Both phrases are standard in modern French. Une huitaine and une quinzaine are related nouns meaning “about a week” and “about a fortnight.” English equivalents are “a week” and “a fortnight” or “two weeks.”