French Time Prepositions: When to use à, en, and dans

• en + duration: refers to the total time spent completing an action. J'ai lu le livre en deux jours (It took me two days to read the book).
• dans + duration: refers to the time until an action begins or happens. Je lirai le livre dans deux jours (I will read the book in two days [from now, meaning I will start reading then]).

Generally, no, not to indicate "on Monday" in a statement. For example, you say Lundi, je travaille (On Monday, I work) or Le lundi, je travaille (On Mondays, I work). However, à is used in common expressions like À lundi ! (See you Monday!) or À demain ! (See you tomorrow!). In these cases, à implies a specific future meeting point rather than an event happening on that day.

It is always à midi (at noon). Midi is treated as a precise, fixed point in time, similar to a specific clock hour. Using en midi is grammatically incorrect in this context and would not be understood as "at noon." The same applies to à minuit (at midnight).

Yes, when dans is used with a time expression (e.g., dans une heure, dans deux jours), it strictly refers to a future point in time, indicating a delay or a countdown before something occurs or begins. It means "in X amount of time from now."

For general parts of the day, you typically use the definite article le with the noun: le matin (in the morning), l'après-midi (in the afternoon), le soir (in the evening), la nuit (at night). For example, Je bois du café le matin. (I drink coffee in the morning.) Avoid en matin or à matin for these general expressions. Specific situations might use en matinée or en soirée but are usually reserved for cultural events or very specific segments of the day, not general habits.

Yes, always. When referring to a specific year, en is the only correct preposition. For example, en 2000, en 1989, en l'an 2000 (in the year 2000, though en 2000 is more common). You will never use à or dans directly before a year number to mean "in X year."

Yes, dans is also a preposition of place meaning "in" or "inside of." For example, Je suis dans la maison. (I am in the house.) This can sometimes be confusing for learners because of its dual function. However, the context will always make it clear whether you are talking about time or location. In this lesson, we focused exclusively on its temporal use. Just remember that its core meaning of being "within" or "enclosed by" extends to both time and space.

While both relate to duration, they have subtle differences. en (as discussed) refers to the time taken to complete an action, often emphasizing efficiency or the full duration of a completed task. J'ai lu le livre en deux heures. (It took me two hours to read the book.) pendant means "during" or "for the duration of" and focuses on an action that occurred throughout a period, often without emphasizing completion within that specific timeframe. J'ai lu le livre pendant deux heures. (I read the book for two hours – implying I spent two hours reading, but not necessarily finished it.) For A1, the key distinction is en for completion duration and dans for future countdown.