Most of you know me. If I thought a Tally Table would be the best thing for this problem, I'd be on it like white on rice. The Tally Table and all of it's wonderful different renditions are not the way to go on something like this, IMHO.
I'll also state that I've not done a performance comparision with any of the code offered, so far. I can only state that I've done previous comparisons and I've found one bit of code that, at the time, blew away the competition. That code comes from Itzik Ben-Gan and may be found at the following URL. Like SSC, it requires simple spam-free membership but it's absolute worth the time to sign up.
Here's the URL for "Packing Date Intervals" such as what is being done on this thread.
http://www.solidq.com/sqj/Pages/2011-March-Issue/Packing-Intervals.aspx
--Jeff Moden
Change is inevitable... Change for the better is not.