using "a" "por" and "en" for parts of the day

Question

Are there certain countries (e.g. Costa Rica) in which "a" is not used for talking about certain parts of the day like morning, afternoon and evening but only por manana or en la manana would be used. Seethe example below?
A la mañana desayuno cereales.I have cereal for breakfast in the morning.

Silvia Píriz · Accepted Answer

Hola Denise B.
Thanks for your question! This isn't really a country-specific difference. The three prepositions a, por and en can all be used with parts of the day, but they express slightly different meanings and are used in different contexts.

Por la mañana is the most common way to mean "in the morning."
En la mañana is also used in many regions, especially in Latin America.
A la mañana is less common overall, but it is perfectly natural in some areas and is used to refer to something that happens during the morning or in the morning.

So, although preferences vary somewhat by region, a la mañana is not exclusive to any one country, nor is it considered incorrect. The choice depends more on regional usage and context than on strict grammar.
Saludos
Silvia