Use a to signal an exact time. The structure is verb + a + time. It appears with on-the-hour times, with minutes and with expressions like a mediodía or a medianoche. In Spanish, the hour is introduced by a when it answers the question ¿a qué hora?.

We arrive a las tres. The class starts a las 7:30. The meeting ends a medianoche. If you replace a with another preposition, the time stops sounding exact and the phrase changes meaning. To see other frequent prepositions, check Common Prepositions.

Use of a with exact hours

Usage	Explanation
Exact time	It is used to indicate an exact time when we talk about a concrete moment on the clock.
Exact minutes	It is also used with exact minutes to say the time in more detail.
Punctual appointment	It is used for a fixed appointment or activity that starts at a specific time.

Use en to locate an event within a month, a season or a year. The normal sequence is verb + en + month, season or year. That’s why you say en mayo, en verano and en 2025.

It is also used with broad dates when the moment belongs to that period. I was born in April. It’s cold in winter. We moved in 2019. If you want to express location, the same preposition can fulfill another different function; that difference appears in Locaciones prepositivas.

Use of in with months, seasons, and years

Usage	Explanation
Months	It is used to indicate a month in which something happens.
Seasons	It is used to talk about a season of the year.
Years	It is used to mention a concrete year.

With parts of the day, en places the action within a daily span. It is used in en la mañana, en la tarde and en la noche. The preposition does not mark an exact hour, but a broad temporal block.

I work in the morning. We go out in the afternoon. Study in the night. When Spanish wants a precise hour, use a; when it wants a general span, use en. That opposition also appears in Preposiciones.

a la mañanaen la mañanapor la mañana

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Se usa para hablar del tramo de la mañana en una variedad muy frecuente en MéxicoSe usa para hablar del tramo de la mañana en una variedad muy común en ArgentinaSe usa para hablar del tramo de la mañana en la variedad más habitual en España

Parts of the day by regional variety

Region	Variant	Definition	Example
Spain	por la mañana	It is used to talk about the morning period in the most common variety in Spain.	Estudio mejor por la mañana.I study better in the morning.
Mexico	en la mañana	It is used to talk about the morning period in a very common variety in Mexico.	Tomo café en la mañana.I drink coffee in the morning.
Argentina	a la mañana	It is used to talk about the morning period in a very common variety in Argentina.	Salgo a correr a la mañana.I go out to run in the morning.

Scramble

Some expressions of time carry de because the preposition is part of the fixed expression. It isn’t chosen freely by general meaning; it is learned together with the phrase. This happens in expressions like de vez en cuando, de repente, de noche and de día.

I come de vez en cuando. The rain started de repente. We stroll de noche. The temporal sense is complete only with the whole expression. In these cases, removing de breaks the usual form of Spanish. Later you’ll see similar structures in Locuciones prepositivas.

Fixed expressions with de

Idea
It is used as part of fixed time expressions and is not replaced by another preposition.
It is used in memorized expressions that sound natural as complete chunks.
It is used in traditional formulas that are best learned as they are.

Desde marks the starting point and hasta marks the ending point of a period. The structure is desde + start + hasta + end. Both prepositions delimit the complete time span.

The store opens from eight to ten. We live here from 2020 to 2024. I’ll be busy from Monday to Thursday. If only desde appears, the start is understood; if only hasta appears, the final limit is understood. These two prepositions also form part of the general system of Preposiciones.

Start and end of a time period

Usage	Explanation
Start of the period	It is used to mark the point at which something begins.
End of the period	It is used to indicate the final limit of an action or stage.
Whole span	They are used together to enclose an entire time interval.

Use durante when an action occurs across an entire period. The structure is verb + durante + time. The preposition doesn’t indicate an start or end, but a continuity within that span.

We sleep during the trip. It rained throughout the night. I worked for two years at that company. The focus is on the full duration of the action within the mentioned period. If the goal is to indicate entry or exit from an interval, other prepositions like desde and hasta are used. To compare similar values in Spanish, it also helps to review Common Prepositions.

Continuous duration with during

Usage	Explanation
Sustained action	It is used to indicate that something occurs throughout an entire period.
Full period	It is used when the action continues without significant interruption.
Waiting time	It is used to talk about a duration that accompanies another activity.

Use por when the duration isn’t exact or when an action occurs around a time span. The preposition expresses approximation, not a precise limit. It appears in phrases like por la mañana, por unos minutos, por varios días or por esas fechas.

I leave in the morning. It was closed for three days. He arrived around those dates. The idea is a wide, nearby or estimated time zone. It does not mark the exact start or end of the period. In contrast with more precise expressions, por leaves the duration open. At this point it is also useful to distinguish it from directional prepositions, treated in Preposiciones de Dirección.

Use of por for approximate duration

Usage	Explanation
Imprecise duration	It is used when the amount of time is approximate and we do not want total precision.
Time span	It is used to refer to a nearby or estimated span.
Temporal explanation	It is used to situate something within a time margin.

Antes de expresses anteriority and después de expresses posteriority. The structure is antes de + event or moment and después de + event or moment. These forms place an action relative to another.

We arrived before the meeting. We ate after working. Call before leaving. See you after class. When the verb that follows has its own subject, the full form is kept: después de que + verb. To expand the Spanish preposition system, check Preposiciones and Locuciones prepositivas.

Anteriority and posteriority in time

Usage	Explanation
Anteriority	It is used to say that something happens before another action or moment.
Posteriority	It is used to say that something happens after another action or moment.
Order of actions	They are used to order two moments in a temporal sequence.