Learn Spanish (Latin America): Son las seis, empieza a oscurecer y eso me desespera. - It is six o'clock, it is starting to get dark, and that drives me to despair.

Eso is a neuter pronoun. You use it when referring to an abstract idea, a general situation, or an entire previous statement rather than a specific masculine or feminine noun. Here, it refers to the whole situation of it being six o'clock and starting to get dark.

Why is it "empieza a oscurecer" and not just "empieza oscurecer"?

The verb empezar (to begin or start) always requires the preposition a when it is followed by an infinitive verb. This forms a common verbal phrase used to indicate the beginning of an action.

How is the word "oscurecer" formed?

Oscurecer (to get dark) is formed from the adjective oscuro (dark). In Spanish, you can often create verbs that describe a change of state by adding the suffix -ecer (and sometimes a prefix like en-) to an adjective. Other B2-level examples include enriquecer (to get rich) from rico, or enrojecer (to turn red) from rojo.

Does "desesperar" mean "to make someone desperate"?