Google recently added a set of options to the search result page. After you do a search a link with "Show Options" appears near the top of the results. When you click on this, you will get some nifty new options for customizing the search you just did.
I find the "Any time" feature. Now you can see results that are "Recent", the "Past hour", "Past 24 hours", "Past week", "Past year", or even pick a "Specific date range". Of course this would be pages that Google has actually found and indexed. If you posted something 2 hours ago and try to find it using the "Past hour" feature don't expect to find it. This would be more along the lines of sites and pages Google has indexed within the "Past hour".
Whether this is part of the new Google Caffeine Search that is in beta right now or not is not known. It does appear that Google is making several new changes and updates lately. You never know what Google is up to and will put our next. I do think that Google Caffeine, a sort of update to Google's regular search is in response or related to Microsoft's recent release of Bing that is gaining popularity.
Here I search for Dogs in Google:
Here are the results, notice the "Show options" link:
When I click on "Show options" now I have a new set of additional features: