Thanks for the great hack, this is exactly what I was looking for. I can't believe that they still haven't added this feature to the standard vbulletin, even in the v3 beta.
I made a few tweaks to the searchinfo template code that you may want to change in the original. I think the following lines have the text in the wrong place. The "To search for all..." text does not appear in the same size or color as the other search page tables.
Code:
<td bgcolor="#1D6AA0"><b>To search for all posts by xx days click below</b>
<smallfont color="#EEEEFF"></smallfont></td>
I think this should be:
Code:
<td bgcolor="#1D6AA0"><smallfont color="#EEEEFF"><b>To search for all posts by xx days click below</b>
</smallfont></td>
Also, at least on my server, it was not necessary to specify the full URL for the daysearch.php file. The following was sufficient.
Code:
<a href="daysearch.php">
This change will eliminate the need for people to modify this line.