For instance, consider the sentence, "I ate lunch today." Is it necessary or acceptable to put a comma before "today?"

Generally speaking, some of these time phrases look wrong to me when used with a comma, while others do not. I think the central question and the source of my confusion is, "When is the time not critical to the meaning of the idependent clause?" Is there a better rule of thumb?

  • "I ate lunch, today."
  • "I ate lunch, while the others were out."
  • "I ate lunch, at the same time the others did."

2 Answers 2


In your 3 examples, the one sentences who requires the comma is the number 3. Let's see:

  • "I ate lunch, today." - VS - "I ate lunch today."

In this case you normally wouldn't put a comma, as there's no need. The second one is perfectly uacceptable. But if you put a comma, you would emphasise "today". So it might sound like "I normally don't eat lunch but today I did".

  • "I ate lunch, while the others were out." - VS - "I ate lunch while the others were out."

Here the same more or less, but the sentence without comma still sounds understandable. Although if you put it, it will sound much more clear, and in that case, it won't hurt.

  • "I ate lunch, at the same time the others did." - VS - "I ate lunch at the same time the others did."

Here it's the same. Without comma it sounds different than with it, but it still makes sense.

  • So, with short sentences you can leave it out, but if it makes the meaning clearer with 2 clauses, put it. You can look here for further reference.
  • 5
    I don't think the comma is necessary in the "at the same time" sentence. I'd only add it there for heavy emphasis on the adverbial phrase, if such an effect were required. // In the "while" sentence, I agree that the comma isn't necessary; it would emphasise the "while" clause, thereby probably changing its meaning to adversative: I ate lunch, but the others were out: can you believe it? How dare they? — something like that. Apr 25, 2011 at 12:52
  • @Cerberus: Uhm, yeah, you're right.
    – Alenanno
    Apr 25, 2011 at 13:01
  • @JasperLoy: So am I. Perhaps I might add it in casual contexts, for strong emphasis. But normally I'd not use commas in any of those sentences. It's hard to prove that something is never right... Apr 25, 2011 at 13:41

You should avoid the comma in all three cases. The rule of thumb would be to not use a comma in these situations; there might be times when it's appropriate but they would be rare.

  • 2
    +1 In these examples, the comma is only acceptable/necessary if the time phrase comes first: 'While the others were out, I ate lunch.' (comma necessary)
    – krubo
    Apr 26, 2011 at 3:11

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