There are several completely different issues:
1) When ODP search is updated. That supposedly happens once in a good week, and zero times in a bad week. That affects the "search" box at dmoz.org, but has no effect on Google at all.
2) When Google DIRECTORY is updated. That supposedly happens once in a good month, if there is no problem with the RDF that the ODP generates.
3) Google SEARCH doesn't update in a batch. It spiders dmoz.org AND directory.google.org on a regular (maybe daily) basis, and reflects changes almost immediately after that. It doesn't even know about ODP search, and it doesn't know about ANY directory updates, it just checks individual pages on a very regular basis.
There's an article by Jean Manco at
http://jean.manco.googlepages.com/googleanddmoz -- if you're interested in clearly understanding the concept rather than knowing what happened yesterday afternoon, it's still recommended.