In an earlier post I suggested that the semantics of a noun or referring phrase does not include time. The sense of time is what a verb brings in. Hence past, present and future tenses, and hence qualifying adverbs like 'now' and 'then'. This avoided the philosophical difficulty about treating the ship composed of the old planks ('the ship as it was then') being any different from the ship composed of the new planks ('the ship as it is now').
But perhaps there is a difficulty, indicated by the distinction between the simple past tense (the ship was composed of the old planks) and the perfect tense (the ship has been composed of the old planks). The distinction (though familiar and its ordinary usage well understood*) is not philosophically clear, and grammar books tend to fudge the explanation. But it seems to be: we use 'has been F' as a predicate to qualify the object 'as it as now', and 'was F' to qualify the object 'as it was then'. Otherwise the grammatical distinction makes no sense. It must distinguish something, and the distinction seems to be the philosophically dangerous one that I said we should avoid.
A similar distinction is evident in the difference between 'in 10 years time people will have a better standard of living' and 'in a 100 years' time, people will live for much longer'. In the first 'people' apparently ranges over people who exist now. In second, it clearly ranges over people who have not been born yet, but will exist in the future. Perhaps there is some notion of tense built into the subject of a proposition. But it's puzzling, and there is not much I can say about it, as things are now.
* The idea for this post came after reading a paper by Braakhuis, who wrote 'In 1940 Grabmann has drawn attention to this collection'. The use of the perfect, rather than the simple past, misleadingly suggests that Grabmann is still alive, which he isn't (he died in 1949).