Determine Whether Two Time Ranges Overlap?

When it occurred to me that I needed to calculate this, I knew it was over my head. (although I did come up with what I thought to be a pretty clever solution involving a very complex series of arrays...) So I decided to google it. The trouble is, the solution was a little over my head too... So I hacked away at it for about an hour, and finally it worked, but on closer inspection I had made a typo from the original algorithm.

Is the original algorithm correct, or flawed? is my interpretation correct/flawed, or the same? I'm not really sure what I did here, but after many tests, I think I got the correct solution.

original post on [URL] Let CondA Mean DateRange A Completely After DateRange B (True if StartA > EndB) Let CondB Mean DateRange A Completely Before DateRange B (True if EndA < StartB)

Then Overlap exists if Neither A Nor B is true ( If one range is neither completely after the other, nor completely before the other, then they must overlap)

Now deMorgan's law, I think it is, says that

Not (A Or B) <=> Not A And Not B

Which means (StartA <= EndB) And (EndA >= StartB)

NOTE: This includes conditions where the edges overlap exactly. If you wish to exclude that, change the >= operators to >, and <= to <

And finally the test scenario that I finally got to work:

<input onclick="this.value=''" onkeyup="TEST()" id=inhour1 value=1>
<input onclick="this.value=''" onkeyup="TEST()" id=inminute1 value=1>
<br />
<input onclick="this.value=''" onkeyup="TEST()" id=outhour1 value=2>

[Code]....