Una vez que: once
Una vez que says that one thing has to happen before the next can: once. It follows the rule of cuando: the subjunctive for the future, the indicative for facts and habits. You already know una vez + participle (una vez terminado el trabajo); una vez que takes a full verb.
| Once you guys have the keys, you can come in whenever you want. | Una vez que tengáis las llaves, podéis entrar cuando queráis. |
Future, so tengáis.
| Once we got to the hotel, we went to sleep. | Una vez que llegamos al hotel, nos fuimos a dormir. |
A fact, so llegamos.
Apenas: hardly, or as soon as
You know apenas as hardly. At the head of a time clause it means as soon as, like en cuanto, with the same choice of mood.
| hardly | as soon as |
|---|---|
| Esta semana apenas he dormido. | Apenas llegué a casa, empezó a llover. |
| As soon as I got home, it started to rain. | Apenas llegué a casa, empezó a llover. |
A past fact: indicative, and the comma marks where the time clause ends.
| As soon as I know something, I'll call you. | Apenas sepa algo, te llamo. |
Still to come: subjunctive, exactly as with en cuanto sepa.
En cuanto is the everyday choice; apenas often sounds a little more formal.
En el momento en que
En el momento en que, also en el momento que, is the moment (that).
| The moment I saw her, I knew it was her. | En el momento en que la vi, supe que era ella. |
Supe here is I knew at once, the preterite of saber.
| The moment you have the results, let me know. | En el momento en que tengas los resultados, avísame. |
The results are not here yet, so tengas.
Finished first: cuando hayas terminado
When the time clause has to be over before the main action, Spanish often uses the perfect subjunctive (haya + participle), like English when you have finished. It works with cuando, en cuanto, una vez que, apenas and hasta que.
| When you have finished, call me. | Cuando hayas terminado, llámame. |
First you finish, then you call.
| I won't leave until you have told me the truth. | No me iré hasta que me hayas dicho la verdad. |
The truth has to come out before I leave.
The present subjunctive is usually fine too (cuando termines, llámame); hayas terminado stresses that it has to be done first.
