Have a look here, 3.4b - Commas with Adverbial Clauses. Scroll down to More on adverbial clauses at the end of a sentence...
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This situation began to change in the 1980's when the number and the variety of foreign pople increased and when Japanese became an internationally popular language.
Should a comma be put before the first when? If a comma exits there, how is the meaning different?
Thank you very much.
Thanks Casiopea for answering my question again.
Yes, my question is whether you can restirict the 1980's by the relative adverb when. Strictly speaking, as in "Modern Athens was born in 1834, when the city was restored as the capital of a newly independent Greece," I think you should put a comma there, but I googled putting "was born in * when" I have had many results in which there is not a comma before when. I learned the reason why you need a comma there becasue if there isn't a comma, for instance, in the example sentence, as if it sounds like there were another 1834. What do you think about? Does it sound so. Another reason why I insit on it is, a stupid reason, when we traslate them into Japanese, there are differences beween the restrictive and the non-restrictive as we basically have to translate restricting parts like modifying the restricted part. Do you feel restricting parts modify restricted parts or no? I would like to know the native speaker's sense.
Try looking at is this way,
Ex: Modern Athens was born at a time when the city was restored as the capital of a newly independent Greece.
Ex: Modern Athens was born in 1834, at a time when the city was restored as the capital of a newly independent Greece.
Ex: Modern Athens was born in 1834, when the city was restored as the capital of a newly independent Greece.
Modern Athens was born in 1834, when the city was restored as the capital of a newly independent Greece. Greek refugees flooded the city at the end of the ... Source Himalayan and worldwide treks, walks and cultural tours
Does that help?
So the 1980's should be punctuated, strictly speaking, I think. There is no other the 1980's and 1834. Probably, the way a comma is not used is informal. But, don't you think, another my question, a comma is not so important for native speakers, I mean, does it have a restricted or non restricted feeling? How about you Casiopea, I would like to know the sence of words of native speakers.
I rememer the day when we first met. This is ok. Because there are many other days. You can restrict and modify the day.
Ex: I remember the day when we first met. <restrictive>
Ex: I remember the day we first met. <omit when>
Ex: I rememer when we first met. <omit the day>
Your example sentence:
The situation began to change in the 1980s, (i.e., which (by the way) was a time) when...
The situation began to change in the 1980s when (i.e., because) the number and variety of people increased ...
Does that help?
So, is basically OK to restrict the exact time like 1984 or the 1980's? Do you Casiopea feel the no-comma when means because?
Yes, it's OK to use when to head a restrictive clause. The question, though, is this. Does when modify change or 1980s? If the former, then the relative clause is connected to the main verb; if the latter, the relative clause is connected to when the change took place, not why it took place, hence because.
Does that help?
Note, I'm sorry if my replies aren't all that clear this evening. I'm down with a cold.
Thank you very much for answering my questions when you catch a cold. My question is not whether when can head a relative clasue but whether antecedents like 1984 or the 1980's can be restricted by when. And I had no idea that when can modify a verb.
More like, the situation changed when ...