Verbs:Das Passiv in der Vergangenheit
Voice is a grammatical category that describes the relationship between a verb and its subject. As outlined in Passiv im Präsens, if the subject is acting, the voice is active, but if the subject is being acted upon, the voice is passive. The passive voice is used when there is a general subject (e.g., people, one) or when the agent of the action is not known or not important.
Passive voice is used mostly in journalistic or scientific writing, and is a rather formal stylistic element.
In the first example above, the man (i.e., the agent) steals the lamb's lettuce (i.e., acts upon the direct object). In the second example, the agent is not named (if you were the man, would you want anybody to know what you did??); the new subject is the lamb's lettuce: we know that it was stolen. The emphasis is what was stolen, and what happened rather than who did the stealing. That comes later, when the man has his comeuppance ...
Stating the agent in a passive construction - with the use of the dative preposition von (by) or the accusative preposition durch - is the same in the past tense as in the present tense.
The agent is a person or persons:
The agent is an inanimate force (i.e., the weather):
In the simple past tense, the auxiliary verb werden is conjugated in the simple past (i.e., wurde, wurden, etc.). You may remember that the simple past - das Imperfekt - is used mostly in written or formal narratives. In spoken language people typically avoid the passive, or if they use it in the past tense, they use the present perfect form (see below).
In the present perfect tense, the auxiliary verb werden is conjugated in the present perfect (i.e., ist geworden, sind geworden, etc.). However, the past participle geworden is always abbreviated as worden in the passive voice.
If a speaker cannot avoid the passive voice in spoken language, this conversational past form - das Perfekt - is used instead of the Imperfekt form, which is the more formal of the two (see above).