Learn Spanish (Latin America): Es necesario que descanses en cuanto termine esta jornada larga. - It is necessary that you rest as soon as this long workday finishes.

The phrase en cuanto (as soon as) introduces an action that hasn't happened yet (the workday finishing). When temporal phrases like en cuanto, apenas, or tan pronto como refer to an anticipated future event, they require the subjunctive. If it were a habitual action, like 'whenever the workday finishes', you would use the indicative.

Why is descanses also in the subjunctive? Is that because of en cuanto too?

No, descanses is triggered by the impersonal expression es necesario que (it is necessary that) at the beginning of the sentence. Expressions of necessity, desire, or influence followed by que require the subjunctive because they express a subjective expectation rather than declaring an objective fact.

What exactly does jornada mean in this context? Why not just use día?

While día simply refers to a calendar day, jornada specifically refers to a 'workday', a 'shift', or the duration of a specific activity. Saying esta jornada larga emphasizes the exhausting period of work being completed, rather than just the daylight hours.

Why does the verb termine come before its subject, esta jornada larga?