Breakdown of Die ehemaligen Schüler versammelten sich, als die Zeitkapsel geöffnet wurde.
öffnen
to open
als
when (past single event)
der Schüler
the pupil, the school student
werden
to be (passive auxiliary + past participle)
Questions & Answers about Die ehemaligen Schüler versammelten sich, als die Zeitkapsel geöffnet wurde.
Why do we use als for "when" here instead of wenn?
In German, als is used for a single, specific event in the past, like opening this one time capsule. If this were a recurring event ("whenever the capsule was opened"), you would use wenn, which is also the word used for all present and future "when" statements.
Why does the verb versammelten require sich?
The verb sich versammeln (to gather or assemble) is reflexive in German. While in English you can just say "the students gathered", German requires the reflexive pronoun to show they gathered themselves. Without sich, versammeln implies you are gathering something else, like firewood or signatures.
Why is the verb wurde at the very end of the sentence?
The second half of the sentence is a subordinate clause introduced by als. In German subordinate clauses, the conjugated verb (here, the simple past passive helper verb wurde) must be pushed to the very end, placing it after the participle geöffnet.
If we put this past-tense event into reported speech, how do the verbs change?