The time expressions after, before and when are used to indicate when something happens in the past, present, or future. Each is a subordinating conjunction which introduces a dependent clause and can be used at the beginning or in the middle of a sentence. I went to school after I had finished my homework.
How would using past perfect in a 'by the time' clause affect the meaning differently from using the common formula (past simple in the 'by the time clause' plus past perfect in the main clause). For example, what could the following mean? By the time he had finished dinner, it was time for bed.
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