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The bot you've seen is probably the one known as FreshBot. It searches sites for fresh pages, i.e. pages that have changed in the last couple of days. In the result listings those pages are displayed with a date.
More reading on Google: start here [webmasterworld.com].
Please note that lately the distinction between FreshBot and the Deepcrawler is not that clear anymore. For example, a bit off topic: yesterday I saw a bot with Fresh's IP crawling from page to page on my site. It started at widgets/1.html, which has a link to 2.html, which links to 3.html, et cetera. With a 1-2 minute interval, the bot crawled all pages up to 150.html, the last one in that range. It was really beautiful ;) , but is was not old fashioned FreshBot behaviour.
The hits by Google spider go up in count every day. This is good, I guess? but I wonder why the hit number is going up?Is it that I change data on that many pages.
Regarding the number of hits going up: usually it's a good sign, I guess. But there will be days without Googlebot visiting, which is no cause for panic. In the end, the only thing that counts is the traffic Google gives your site.