The preposition at is used to place an exact moment. It accompanies an hour, a precise instant or a very clear reference point such as at noon, at midnight, at 8 o'clock or at that moment. It answers the question of the exact moment, not that of duration. In a sentence like The train leaves at 7 o'clock, at places the departure at a precise time. Without this preposition, the time information disappears or becomes incomplete. With days and dates, this same usage is not used, because at remains connected to a precise point in time.

Usage of à for the precise time

Usage	Explanation
Exact time	We use à to indicate a precise moment in the day.
Fixed reference point	We use à to talk about a clear time reference such as noon or midnight.
Expected time	We use à when giving the scheduled time of an appointment or departure.

In often marks the season, month or year. We say in summer, in January, in 2026. With a season or year noun, in places the action within a broad period. It is also used to express the time needed to do something, when we want to say how long the action takes before being completed. We say He read the book in two days or The journey takes one hour. In this usage, in emphasizes the result achieved within a given duration. For the season, month or year, in indicates the time frame; for duration, it indicates the time needed to reach the end.

Usage of en for seasons and duration

Usage	Explanation
Season	We use en to talk about a season.
Month	We use en to place an action in a specific month.
Necessary duration	We use en to say the time needed to do something.

In refers to a future moment situated after a delay. We say in three days, in a week, in two hours. The starting point is the present, then an interval passes before the event. The appointment is in ten minutes means that ten minutes still have to pass. With in, we look toward the future and measure the time remaining before the action. The preposition does not mark a duration in progress; it marks the wait before the moment arrives.

Usage of dans for a future delay

Usage	Explanation
After a delay	We use dans to talk about an event that will take place after a certain delay.
Time remaining	We use dans to indicate the time remaining before a future action.
Future projection	We use dans to place an action in the future from the present.

For presents the entire duration of an action or event. It is used when we want to say that something lasts throughout a certain period: for an hour, during the holidays, during the meeting. The sentence emphasizes the action occupying this period from beginning to end. He slept for the entire journey shows that sleep occupied the whole journey. For answers the question of the time traversed by the action, not the moment of departure or the moment of arrival.

Usage of pendant for complete duration

Usage	Explanation
Total duration	We use pendant to show the entire duration of an action.
Continuous action	We use pendant for an action that takes place without interruption over a given period.
Limited event	We use pendant to signal that an event lasts over a defined period.

Since indicates that an action began in the past and continues in the present, or that a state still exists now. We say I have lived here since 2020, He has been waiting for an hour, It has been raining since this morning. The duration is counted from a past starting point and reaches the present. Since is used with a clearly established beginning, such as a date, day, hour or event. The form shows that the situation is not over; it is still valid at the moment when we speak.

Usage of depuis for a duration that began

Usage	Explanation
Beginning in the past	We use depuis to say that an action began in the past and still continues.
Starting point	We use depuis to specify the starting time of a current situation.
Ongoing situation	We use depuis to emphasize an action that is still true when we speak.

For expresses a planned duration, a time objective or a period fixed in advance. We say I am leaving for three days, She is working for a year, The contract is valid for six months. Here, the duration is announced as a limit or as a framework fixed in advance. For is also used to present a temporal intention: He is coming for the weekend shows the purpose of the visit in time. In this usage, the sentence does not describe a duration already experienced, but a planned or chosen duration.

Usage of pour for an intended duration

Usage	Explanation
Intended duration	We use pour to indicate the announced duration of an action or stay.
Intention	We use pour when talking about an action done for a specific purpose.
Determined period	We use pour for a period limited and announced in advance.

Ago places an event in the past from the present. We say Two days ago, we ate here, A month ago, she moved. The reference point is now, and the expression moves backward to measure the time elapsed. Ago is used to date a past event, not to show an action that continues. With this form, a fact is placed in a past chronology by indicating how much time has elapsed since it took place.

Usage of il y a for the past

Usage	Explanation
Elapsed past	We use il y a to place an event before the present moment.
Starting moment	We use il y a to say how long ago a fact occurred.
Time gap	We use il y a to express an interval in the past.

Until marks the final limit of a time, schedule or period. We say until noon, until tomorrow, until the end of the month. The action continues and stops at the indicated point. We walked as far as the station shows the destination as the limit reached. With time, until sets the last moment of validity or action. It can introduce an hour, date, event or precise reference point that closes the period.

Usage of jusqu à for the limit

Usage	Explanation
End of a period	We use jusqu à to mark the end of an action or period.
Spatial or temporal limit	We use jusqu à to show the limit reached.
Final point	We use jusqu à to indicate the latest possible moment.

The structure from... to... indicates a complete interval between a starting point and an endpoint. We say from 8 o'clock to 10 o'clock, from January to March, from Monday to Friday. The first element gives the beginning, the second gives the end. When the article is mandatory, the contracted form appears: from the... to the... with a singular masculine noun, such as from morning to evening, from May 3 to 10. This structure serves to precisely frame a period and show its two boundaries.

Rules for de à for the interval

Idea
We use de followed by à to frame a time interval.
We contract de le to du before a singular masculine noun.
We contract à le to au in the same structure.

Some time references are used directly, without a preposition, especially with date or calendar verbs. We say We are leaving Monday, I saw him on April 12, She is arriving tomorrow. In these cases, the time word directly follows the verb or sentence without at or in. For a habit, on is used before the day: on Mondays, I work late, on Saturdays, we sleep longer. Here, on turns the day into a habitual and repeated moment. A single day and a precise date remain without a preposition, whereas a habit takes on.

Rules for days and dates without a preposition

Idea
We use the day or date without a preposition when they serve as a precise reference point.
We put le before a day to express a habit.
We use le before a complete date in common usage.