"There were three explosions in one day."
Il y a eu trois explosions ___ une journée.
Should we use en or dans, or do both work?
French Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the French language. It only takes a minute to sign up.Sign up to join this community
With une journée (one day), en is expected:
Il y a eu trois explosion en une journée. (… in one day)
En is used here to specify the amount of time that was necessary for the three events to occur.
However, if the last part of the sentence had been la journée, dans would have been used:
Il y a eu trois explosions dans la journée. (… during the day/through the day)
Dans means here "inside", not inside a given space which is the main acception for dans but inside a given period of time.
See the very same difference in these sentences:
La petite aiguille fait 24 fois le tour du cadran en une journée.
The minute hand makes 24 turns of the dial in one day.
Il y a 24 heures dans une journée.
There are 24 hours in one day.
Il y a eu trois explosions en vingt-quatre heures. (… during a period of 24 hours)
Il y a eu trois explosions dans la même journée. (… in a single day)
Note that dans can also be used to tell the time that will elapse before some event occur:
Dans trois jours, on vide la piscine.
Three days from now, we'll empty the swimming pool.
En trois jours, on vide la piscine.
To empty the swimming-pool, we need/take three days.