Time and purpose clauses — and the subjunctive that future time demands
The headline rule of B2 Spanish: after cuando (and other time links) referring to the future, the verb goes in the subjunctive. English just uses the present — Spanish marks the unreality.
Cuando llegues, llámame. (When you arrive, call me — arrival hasn't happened yet.)
Compare habit: Cuando llego a casa, ceno. (When I get home, I have dinner — indicative, routine.)
Future reference → llegues (subjunctive). Habit or past → indicative. This contrast is pure B2 exam material.
The same rule covers the whole family of time connectors.
en cuanto (as soon as) — En cuanto sepa algo, te aviso.
hasta que (until) — Espera aquí hasta que vuelva.
antes de que (before) — Sal antes de que llueva. (ALWAYS subjunctive)
después de que (after) — Después de que termines, hablamos.
antes de que is special: it takes the subjunctive even for past events — the "before" event is always unrealised at that point.
Purpose clauses with para que (so that) always take the subjunctive — the goal is wished, not yet real.
Te lo explico para que lo entiendas. (I'm explaining so that you understand.)
Habla más alto para que te oigan. (Speak up so they can hear you.)
Same subject? Drop que and use the infinitive: Estudio para aprobar (I study to pass) — not "para que yo apruebe".
Aunque + indicative states a known fact ("although"); aunque + subjunctive concedes a possibility ("even if").
Aunque llueve, vamos a salir. (Although it IS raining — I can see it — we'll go out.)
Aunque llueva, vamos a salir. (Even if it rains — who knows — we'll go out.)
One vowel changes the meaning: llueve = fact, llueva = hypothesis. Examiners adore this pair.
Some connectors carry conditions: mientras (as long as) and siempre que (provided that) take the subjunctive when they mean a condition.
Puedes salir siempre que vuelvas antes de las doce. (You can go out provided you're back by twelve.)
Mientras vivas en esta casa, seguirás mis reglas. (As long as you live in this house...)
Time meaning ("while") → indicative: Mientras yo cocinaba, él ponía la mesa. Condition → subjunctive.
Traps for English speakers
These are the errors English speakers make most often.