comma before 'when'? is it correct?

Futurehuman11 wrote:

That fight comes in 10 days, when Lesnar takes on former UFC heavyweight champ Frank Mir in the co-main event of UFC 81.

I don't think a comma is required.

Hi Yoong Liat,

Usually I agree with you completely, but the situations you write about above are not parallel to the original poster.

I'll come when I've done the winding up. This isn't the same as I'll come at 2, when I should have finished the [whatever winding up is].

In the original post, it names a time - in 10 days. The rest of the sentence gives more information about that happens at that 10-day point.

I'm looking forward to the day I turn 18, when I can finally vote.
I'll be there at 3, when school lets out.

Futurehuman11 wrote:

That fight comes in 10 days, when Lesnar takes on former UFC heavyweight champ Frank Mir in the co-main event of UFC 81.

This is similar to the case of the second clause renaming the first.

My teacher, Mrs. Smith, is the first English teacher I've had that didn't use 'is' with a plural subject!

We renamed "my teacher", so we use a comma.

... 10 days, when Lesnar...

This time, rather than re-naming (or rather, re-specifying) a person or object, we're renaming a time frame.

I must comment, however, on the odd grammar of the first clause. "That fight comes in 10 days..." sound wierd to me. If I were to write that whole sentence, it'd look like this:

Lesnar takes on former UFC heavyweight champ Frank Mir in UFC 81 in ten days! or Ten days from now, Lesnar takes on ...

Unless there's a context this sentence was pulled out of?